Reference signal patterns based on relative speed between a transmitter and receiver

ABSTRACT

Methods, systems, and devices for wireless communications (e.g., vehicle to everything systems) are described relating to an adaptive design of demodulation reference signals (DMRS) density based on user equipment (UE) velocity. A UE may send assistance information to a transmitting UE to help identify a DMRS pattern based on the relative speed between the two UEs. Also, the transmitter may determine the adaptive DMRS pattern based on its speed without information of the receiver&#39;s speed. The transmitter may indicate the adaptive DMRS pattern in control information to the receiver. A base station may receive assistance information, and the base station may determine the adaptive DMRS pattern to be used by the transmitting UE based on the received assistance information and then indicate the adaptive DMRS pattern to the transmitting UE. A UE may determine an adaptive DMRS pattern to use based on feedback from the receiving UE.

CROSS REFERENCE

The present Application for Patent is a Divisional of U.S. patentapplication Ser. No. 16/843,797 by MALLADI et al., entitled “REFERENCESIGNAL PATTERNS BASED ON RELATIVE SPEED BETWEEN A TRANSMITTER ANDRECEIVER” filed Apr. 8, 2020, which claims the benefit of U.S.Provisional Patent Application No. 62/833,635 by MALLADI et al.,entitled “REFERENCE SIGNAL PATTERNS BASED ON RELATIVE SPEED BETWEEN ATRANSMITTER AND RECEIVER,” filed Apr. 12, 2019, each of which areassigned to the assignee hereof, and each of which are expresslyincorporated by reference in its entirety herein.

INTRODUCTION

The following relates generally to wireless communications, and morespecifically to reference signal patterns.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform spread orthogonal frequency division multiplexing(DFT-S-OFDM). A wireless multiple-access communications system mayinclude a number of base stations or network access nodes, eachsimultaneously supporting communication for multiple communicationdevices, which may be otherwise known as user equipment (UE).

SUMMARY

A method of wireless communications at a first wireless device isdescribed. The method may include transmitting assistance information toa second wireless device and determining an adaptive reference signalpattern of a reference signal for demodulating data, the adaptivereference signal pattern based on the assistance information.

An apparatus for wireless communications at a first wireless device isdescribed. The apparatus may include a processor and memory coupled tothe processor. The processor and memory may be configured to cause theapparatus to transmit assistance information to a second wireless deviceand determine an adaptive reference signal pattern of a reference signalfor demodulating data, the adaptive reference signal pattern based onthe assistance information.

Another apparatus for wireless communications at a first wireless deviceis described. The apparatus may include means for transmittingassistance information to a second wireless device and determining anadaptive reference signal pattern of a reference signal for demodulatingdata, the adaptive reference signal pattern based on the assistanceinformation.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first wireless device is described. The code mayinclude instructions executable by a processor to transmit assistanceinformation to a second wireless device and determine an adaptivereference signal pattern of a reference signal for demodulating data,the adaptive reference signal pattern based on the assistanceinformation.

A method of wireless communications at a first wireless device isdescribed. The method may include transmitting assistance information toa second wireless device, the assistance information associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof, and identifying a reference signalpattern of a reference signal for demodulating data, the referencesignal pattern based on the assistance information.

An apparatus for wireless communications at a first wireless device isdescribed. The apparatus may include a processor and memory coupled tothe processor. The processor and memory may be configured to cause theapparatus to transmit assistance information to a second wirelessdevice, the assistance information associated with a speed of the firstwireless device, or a location of the first wireless device, or acombination thereof, and identify a reference signal pattern of areference signal for demodulating data, the reference signal patternbased on the assistance information.

Another apparatus for wireless communications at a first wireless deviceis described. The apparatus may include means for transmittingassistance information to a second wireless device, the assistanceinformation associated with a speed of the first wireless device, or alocation of the first wireless device, or a combination thereof, andidentifying a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern based on the assistanceinformation.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first wireless device is described. The code mayinclude instructions executable by a processor to transmit assistanceinformation to a second wireless device, the assistance informationassociated with a speed of the first wireless device, or a location ofthe first wireless device, or a combination thereof, and identify areference signal pattern of a reference signal for demodulating data,the reference signal pattern based on the assistance information.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a speed ofthe first wireless device, and transmitting, as part of the assistanceinformation, a speed value indicating the speed of the first wirelessdevice.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a movementdirection of the first wireless device, and transmitting, as part of theassistance information, a direction value indicating the movementdirection of the first wireless device.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining an absolutemovement direction of the first wireless device, and identifying thedirection value from a direction index based on the absolute movementdirection, the direction index including a map between one or moreabsolute movement directions and respective direction values.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, each of the respectivedirection values may be based on an angular offset from a cardinaldirection or an intercardinal direction. Some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein may further include operations, features, means, or instructionsfor determining an absolute speed of the first wireless device, andidentifying the speed value from a speed index based on the absolutespeed, the speed index including a map between respective speed valuesand one or more absolute speeds, or a range of absolute speeds, or acombination thereof. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the speedindex may be from a set of speed indices.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying aconfiguration of the speed index, where identifying the speed value maybe based on the configuration. Some examples of the method, apparatuses,and non-transitory computer-readable medium described herein may furtherinclude operations, features, means, or instructions for receiving anindication of the configuration of the speed index.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining a locationof the first wireless device, and transmitting, as part of theassistance information, a location value indicating the location of thefirst wireless device.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a zoneidentifier from a set of zone identifiers based on the location of thefirst wireless device, each of the set of zone identifiers beingassociated with a respective geographic area, where the location valueincludes the zone identifier.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a relativespeed between the first wireless device and the second wireless devicebased on the assistance information, where the adaptive reference signalpattern may be determined based on the relative speed.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, identifying the relativespeed may include operations, features, means, or instructions forreceiving, from the second wireless device, an indication of a speed ofthe second wireless device, or a velocity of the second wireless device,or a location of the second wireless device, or a combination thereof,and determining the relative speed based on the received indication.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the relativespeed may include operations, features, means, or instructions fordetermining the speed of the first wireless device, and calculating therelative speed based on the speed of the first wireless device and thespeed of the second wireless device.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the relativespeed may include operations, features, means, or instructions fordetermining a velocity of the first wireless device, and calculating therelative speed based on the velocity of the first wireless device andthe velocity of the second wireless device.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the relativespeed may include operations, features, means, or instructions fordetermining, based on the location of the second wireless device, one ormore zones the second wireless device was located in during a timeperiod, where the received indication includes one or more zoneidentifiers corresponding to respective zones, calculating the speed ofthe second wireless device based on the one or more zones the secondwireless device was located in during the time period, and calculatingthe relative speed based on the speed of the first wireless device andthe speed of the second wireless device.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting, as partof the assistance information, an indication of the relative speed. Someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining theadaptive reference signal pattern based on the relative speed, andtransmitting, as part of the assistance information, an indication ofthe adaptive reference signal pattern.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the adaptivereference signal pattern may include operations, features, means, orinstructions for receiving, from the second wireless device, anindication of the adaptive reference signal pattern, and determining theadaptive reference signal pattern based on the indication.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the adaptivereference signal pattern may include operations, features, means, orinstructions for receiving, from a set of wireless devices, respectiveindications of one or more reference signal patterns, and determiningthe adaptive reference signal pattern based on the one or more referencesignal patterns.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the adaptivereference signal pattern may include operations, features, means, orinstructions for selecting the adaptive reference signal pattern fromone or more reference signal patterns, each of the one or more referencesignal patterns corresponding to a respective relative speed, or a rangeof relative speeds, or a combination thereof.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying aconfiguration of a map between the each of the one or more referencesignal patterns and the respective relative speed, or the range ofrelative speeds, or a combination thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the adaptivereference signal pattern may include operations, features, means, orinstructions for identifying a set of communication links with otherwireless devices, each communication link of the set of communicationlinks being associated with a relative speed between the first wirelessdevice and a respective wireless device, and determining the adaptivereference signal pattern based on the relative speeds of the set ofcommunication links.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying a highestrelative speed from the relative speeds of the set of communicationlinks, where the adaptive reference signal pattern may be based on thehighest relative speed.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for determining an errorrate threshold for transmitting the data over the set of communicationlinks, where the adaptive reference signal pattern may be based on therelative speeds of the set of communication links and the error ratethreshold.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the adaptivereference signal pattern may include operations, features, means, orinstructions for identifying a subcarrier spacing for communicating withthe second wireless device, and determining the adaptive referencesignal pattern based on the subcarrier spacing and a relative speedbetween the first wireless device and the second wireless device.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern may be based on a map between the one or more reference signalpatterns and a respective relative speed, or a range of relative speeds,or a combination thereof, and where the adaptive reference signalpattern may be determined based on the map and the subcarrier spacing.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving firstassistance information and second assistance information from the secondwireless device, each of the first assistance information and the secondassistance information being associated with a respective speed of thesecond wireless device, or a respective location of the second wirelessdevice, or a combination thereof, and storing the first assistanceinformation and the second assistance information at the first wirelessdevice.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for identifying adifference between the first assistance information and the secondassistance information, and determining the adaptive reference signalpattern based on the difference. Some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein may further include operations, features, means, or instructionsfor identifying a periodicity for transmitting the assistanceinformation, where the assistance information may be transmitted inaccordance with the periodicity.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for generating firstassistance information and second assistance information for the firstwireless device, each of the first assistance information and the secondassistance information being associated with a respective speed of thefirst wireless device, or a respective location of the first wirelessdevice, or a combination thereof, identifying a difference between thefirst assistance information and the second assistance information, andtransmitting the assistance information based on identifying thedifference.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for receiving a request totransmit the assistance information, where the assistance informationmay be transmitted in response to the received request.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting the dataand the reference signal to the second wireless device, the referencesignal being transmitted in accordance with the adaptive referencesignal pattern. Some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein may furtherinclude operations, features, means, or instructions for receiving thedata and the reference signal from the second wireless device, thereference signal being received in accordance with the adaptivereference signal pattern.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the assistanceinformation may include operations, features, means, or instructions fortransmitting the assistance information as part of sidelink controlinformation, or as part of a medium access control (MAC) controlelement, or over a sidelink data channel, or over a sidelink sharedchannel, or over a feedback channel, or a combination thereof.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern indicates one or more symbol periods during which the referencesignal may be transmitted and a gap between each of the one or moresymbol periods.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern may be from a set of reference signal patterns, each referencesignal pattern of the set including a different number of symbol periodswithin a slot that include the reference signal.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern may be from a set of reference signal patterns, each referencesignal pattern of the set including a different gap between symbolperiods within a slot that include the reference signal.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for communicating with thesecond wireless device using sidelink communications, where the firstwireless device includes a first UE and the second wireless deviceincludes a second UE. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the sidelinkcommunications may be vehicle to everything communications.

A method of wireless communications at a first wireless device isdescribed. The method may include determining a speed of the firstwireless device, identifying a subcarrier spacing for communicating withone or more other wireless devices, determining, based on the speed ofthe first wireless device and the subcarrier spacing, a reference signalpattern of a reference signal for demodulating data, and transmittingthe data and the reference signal to the one or more other wirelessdevices, the reference signal being transmitted in accordance with thereference signal pattern.

An apparatus for wireless communications at a first wireless device isdescribed. The apparatus may include a processor and memory coupled tothe processor. The processor and memory may be configured to cause theapparatus to determine a speed of the first wireless device, identify asubcarrier spacing for communicating with one or more other wirelessdevices, determine, based on the speed of the first wireless device andthe subcarrier spacing, a reference signal pattern of a reference signalfor demodulating data, and transmit the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

Another apparatus for wireless communications at a first wireless deviceis described. The apparatus may include means for determining a speed ofthe first wireless device, identifying a subcarrier spacing forcommunicating with one or more other wireless devices, determining,based on the speed of the first wireless device and the subcarrierspacing, a reference signal pattern of a reference signal fordemodulating data, and transmitting the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first wireless device is described. The code mayinclude instructions executable by a processor to determine a speed ofthe first wireless device, identify a subcarrier spacing forcommunicating with one or more other wireless devices, determine, basedon the speed of the first wireless device and the subcarrier spacing, areference signal pattern of a reference signal for demodulating data,and transmit the data and the reference signal to the one or more otherwireless devices, the reference signal being transmitted in accordancewith the reference signal pattern.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, transmitting the data andindication of the reference signal pattern may include operations,features, means, or instructions for broadcasting the data and thereference signal to the one or more other wireless devices.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for transmitting anindication of the reference signal pattern to the one or more otherwireless devices. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the indicationmay be transmitted within control information to the one or more otherwireless devices.

A method of wireless communications at a first wireless device isdescribed. The method may include transmitting assistance information toa base station, the assistance information associated with a speed ofthe first wireless device, or a location of the first wireless device,or a combination thereof, receiving, from the base station, anindication of an adaptive reference signal pattern of a reference signalfor demodulating data, the adaptive reference signal pattern being basedon the assistance information, and transmitting the data and thereference signal to a second wireless device, the reference signal beingtransmitted in accordance with the adaptive reference signal pattern.

An apparatus for wireless communications at a first wireless device isdescribed. The apparatus may include a processor and memory coupled tothe processor. The processor and memory may be configured to cause theapparatus to transmit assistance information to a base station, theassistance information associated with a speed of the first wirelessdevice, or a location of the first wireless device, or a combinationthereof, receive, from the base station, an indication of an adaptivereference signal pattern of a reference signal for demodulating data,the adaptive reference signal pattern being based on the assistanceinformation, and transmit the data and the reference signal to a secondwireless device, the reference signal being transmitted in accordancewith the adaptive reference signal pattern.

Another apparatus for wireless communications at a first wireless deviceis described. The apparatus may include means for transmittingassistance information to a base station, the assistance informationassociated with a speed of the first wireless device, or a location ofthe first wireless device, or a combination thereof, receiving, from thebase station, an indication of an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern being based on the assistance information, and transmitting thedata and the reference signal to a second wireless device, the referencesignal being transmitted in accordance with the adaptive referencesignal pattern.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first wireless device is described. The code mayinclude instructions executable by a processor to transmit assistanceinformation to a base station, the assistance information associatedwith a speed of the first wireless device, or a location of the firstwireless device, or a combination thereof, receive, from the basestation, an indication of an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern being based on the assistance information, and transmit the dataand the reference signal to a second wireless device, the referencesignal being transmitted in accordance with the adaptive referencesignal pattern.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern may be from one or more reference signal patterns, each of theone or more reference signal patterns corresponding to a respectivespeed, or a range of speeds, or a combination thereof.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for operating under a modefor sidelink communications, where the first wireless device includes afirst UE and the second wireless device includes a second UE.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the adaptive reference signalpattern includes one or more symbol periods during which the referencesignal may be transmitted and a gap between each of the one or moresymbol periods.

A method of wireless communications at a first wireless device isdescribed. The method may include receiving, from one or more otherwireless devices, feedback information in response to one or moreprevious data transmissions to the one or more other wireless devices,determining a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information, and transmitting the data and the reference signalto the one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

An apparatus for wireless communications at a first wireless device isdescribed. The apparatus may include a processor and memory coupled tothe processor. The processor and memory may be configured to cause theapparatus to receive, from one or more other wireless devices, feedbackinformation in response to one or more previous data transmissions tothe one or more other wireless devices, determine a reference signalpattern of a reference signal for demodulating data, the referencesignal pattern being based on the feedback information, and transmit thedata and the reference signal to the one or more other wireless devices,the reference signal being transmitted in accordance with the referencesignal pattern.

Another apparatus for wireless communications at a first wireless deviceis described. The apparatus may include means for receiving, from one ormore other wireless devices, feedback information in response to one ormore previous data transmissions to the one or more other wirelessdevices, determining a reference signal pattern of a reference signalfor demodulating data, the reference signal pattern being based on thefeedback information, and transmitting the data and the reference signalto the one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

A non-transitory computer-readable medium storing code for wirelesscommunications at a first wireless device is described. The code mayinclude instructions executable by a processor to receive, from one ormore other wireless devices, feedback information in response to one ormore previous data transmissions to the one or more other wirelessdevices, determine a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information, and transmit the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the referencesignal pattern may include operations, features, means, or instructionsfor computing an error rate over a time period based on the feedbackinformation, and determining the reference signal pattern based on theerror rate satisfying an error rate threshold.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the error rate includes ablock error rate or a packet error rate of the one or more previous datatransmissions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, determining the referencesignal pattern may include operations, features, means, or instructionsfor measuring a received power of the feedback information, anddetermining the reference signal pattern based on the received powersatisfying a power threshold.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the feedback informationincludes one or more negative acknowledgments received during a timeperiod.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationsthat supports reference signal patterns based on relative speed betweena transmitter and receiver in accordance with one or more aspects of thepresent disclosure.

FIG. 2 illustrates an example of a wireless communications system thatsupports reference signal patterns based on relative speed between atransmitter and receiver in accordance with one or more aspects of thepresent disclosure.

FIGS. 3A, 3B, 3C, 3D, and 3E illustrate examples of reference signalpatterns that support reference signal patterns based on relative speedbetween a transmitter and receiver in accordance with one or moreaspects of the present disclosure.

FIGS. 4 through 7 illustrate examples of a process flow in a system thatsupports reference signal patterns based on relative speed between atransmitter and receiver in accordance with one or more aspects of thepresent disclosure.

FIGS. 8 and 9 show block diagrams of devices that support referencesignal patterns based on relative speed between a transmitter andreceiver in accordance with one or more aspects of the presentdisclosure.

FIG. 10 shows a block diagram of a reference signal manager thatsupports reference signal patterns based on relative speed between atransmitter and receiver in accordance with one or more aspects of thepresent disclosure.

FIG. 11 shows a diagram of a system including a device that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure.

FIGS. 12 through 18 show flowcharts illustrating methods that supportreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure.

DETAILED DESCRIPTION

Wireless communications devices operating in a system that supportssidelink communications (e.g., a vehicle-to-everything (V2X) system, avehicle-to-vehicle (V2V) system, a cellular-V2X (C-V2X) system, or othertype of device-to-device (D2D) system) may communicate with each otherwhile in motion. For example, a UE within a V2X system may be travelingat a velocity and may attempt to transmit or receive communications witha neighboring UE (e.g., via sidelink transmission) traveling at adifferent velocity to exchange information. In some cases, thedifference in the UE's velocities may span a wide range (e.g., a fewkilometers per hour (kmph) to about 500 kmph), which may make controlinformation transmissions inefficient (e.g., poor quality or excessoverhead signaling). In some cases, efficient transmission of referencesignals (e.g., demodulation reference signal (DMRS)) may vary based onthe relative speed between the UEs. For instance, when a relative speedbetween the UEs is high, techniques may be used to ensure the referencesignals are properly presented (e.g., a higher time-domain density ofreference signals may be present). However, when the relative speedbetween the UEs is low, fewer reference signals in time-domain may needto be transmitted than at higher relative speeds. If the same number ofreference signals are transmitted for high and low relative speeds, theneither the reference signal pattern may be inefficient for high relativespeeds or there may be unnecessary overhead for signaling under lowrelative speeds, or both. This may result in ineffective wirelessspectral use and poor sidelink performance. Therefore, a flexible designof reference signal patterns to ensure accurate and efficient decodingof control or data information (e.g., in channel estimation) at UEs ofvarying velocities may be beneficial.

An adaptive design of DMRS time density based on UE velocity may allowfor an increase in DMRS density when relative speed is high and adecrease in DMRS density when relative speed is low. The DMRS design mayinclude a number of different DMRS patterns of varying densitycorresponding to different speed ranges (e.g., two, three, or four DMRSpatterns and corresponding speed ranges). In some examples, a UE maysend assistance information (e.g., UE's speed, direction, location,relative speed, subcarrier spacing, and/or DMRS pattern index) to thetransmitting UE (which may be referred to herein as a “transmitter,” atransmitting wireless device, or other like terminology) to helpidentify an efficient DMRS pattern based on the relative speed betweenthe two UEs. The transmitter may then transmit the DMRS and data to areceiving UE (which may be referred to herein as a “receiver,” areceiving wireless device, or other like terminology) after thetransmitter determines the DMRS pattern. Assistance information may betransmitted periodically, after a change of assistance information, orbased on a trigger from a transmitter.

In another example, a UE may be unable to send or receive assistanceinformation (e.g., UE's speed, direction, location, relative speed,subcarrier spacing, and/or DMRS pattern index). Thus, the transmittermay determine the DMRS pattern based on its own speed withoutinformation of the receiver's speed (e.g., in a broadcast transmission).The transmitter may then indicate the selected DMRS pattern in controlinformation to one or more receivers followed by a transmission of theDMRS and data. In some cases, the UEs may utilize resources scheduled bya base station (e.g., when operating in mode 1 of sidelinkcommunications). For instance, one or both of UEs may send assistanceinformation (e.g., UE's speed, direction, location, relative speed,and/or DMRS pattern index) to the base station (e.g., gNB). The basestation may determine the DMRS pattern to be used by the transmitting UEbased on the received assistance information and then indicate the DMRSpattern to the transmitting UE. The transmitter may then transmit theDMRS, using the indicated pattern, and data.

In another example, a transmitting UE may determine the DMRS pattern touse with the receiving UE based on hybrid automatic repeat request(HARQ) feedback from the receiving UE. The HARQ feedback may helpdetermine a DMRS pattern by identifying an error (e.g., block error rate(BLER) or packet error rate) that may be compared to a threshold todetermine the DMRS pattern for subsequent transmissions. For example, ifthe BLER is above a threshold, a denser DMRS pattern may be used for thenext transmission in comparison to the previous transmission.Additionally or alternatively, a negative acknowledgement (NACK) may beused to determine received power at the transmitter, and the receivedpower may be compared to a threshold to determine the DMRS pattern forsubsequent transmissions. For instance, if the received power is above athreshold, a denser DMRS pattern may be used for the next transmissionin comparison to the previous transmission. For example, in groupcastcommunications, multiple UEs may fail in decoding and send NACK to thetransmitting UE. In such cases, the transmitting UE may receive arelatively larger NACK received signal power if more UEs send NACK atthe same time (e.g., as compared to receiving a single NACK) becauseNACK signals may be combined over the air. That is, the received powerof NACK at transmitter may be larger if more UEs send NACK. Accordingly,a large received power for NACK may indicate that the transmitting UEmay use a denser DMRS pattern than the previous transmission. Thetransmitter may then transmit the DMRS and data after the transmitterdetermines the DMRS pattern. In some cases, the HARQ feedback may bestored over time such that the error rate or received power for a UE maybe tracked over time.

The UE may determine the DMRS pattern index using a mappingconfiguration. The mapping configuration may indicate a mapping betweena DMRS pattern and a corresponding relative speed range or feedbackthresholds. The mapping may be predefined (e.g., a table is stored atthe UE), preconfigured (multiple tables may be stored at the UE), orconfigured by higher layer signaling (e.g., radio resource control (RRC)signaling). Additionally or alternatively, the DMRS pattern may bedetermined based on a numerology (e.g., a subcarrier spacing) usedwithin a system.

Aspects of the disclosure are initially described in the context ofwireless communications systems. Aspects of the disclosure are furtherillustrated by and described with reference to process flows, apparatusdiagrams, system diagrams, and flowcharts that relate to transmittingDMRS for sidelink communications.

FIG. 1 illustrates an example of a wireless communications system 100that supports reference signal patterns based on relative speed betweena transmitter and receiver in accordance with one or more aspects of thepresent disclosure. The wireless communications system 100 includes basestations 105, UEs 115, and a core network 130. In some examples, thewireless communications system 100 may be a Long Term Evolution (LTE)network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a NewRadio (NR) network. In some cases, wireless communications system 100may support enhanced broadband communications, ultra-reliable (e.g.,mission critical) communications, low latency communications, orcommunications with low-cost and low-complexity devices.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB orgiga-NodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up a portion of the geographic coverage area 110,and each sector may be associated with a cell. For example, each basestation 105 may provide communication coverage for a macro cell, a smallcell, a hot spot, or other types of cells, or various combinationsthereof. In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples,half-duplex communications may be performed at a reduced peak rate.Other power conservation techniques for UEs 115 include entering a powersaving “deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105 or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1, N2, N3, orother interface). Base stations 105 may communicate with one anotherover backhaul links 134 (e.g., via an X2, Xn, or other interface) eitherdirectly (e.g., directly between base stations 105) or indirectly (e.g.,via core network 130). A UE 115 may communicate with the core network130 through communication link 135.

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 megahertz (MHz) to 300gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known asthe ultra-high frequency (UHF) region or decimeter band, since thewavelengths range from approximately one decimeter to one meter inlength. UHF waves may be blocked or redirected by buildings andenvironmental features. However, the waves may penetrate structuressufficiently for a macro cell to provide service to UEs 115 locatedindoors. Transmission of UHF waves may be associated with smallerantennas and shorter range (e.g., less than 100 km) compared totransmission using the smaller frequencies and longer waves of the highfrequency (HF) or very high frequency (VHF) portion of the spectrumbelow 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that may be capable of toleratinginterference from other users.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band such as the 5 GHz ISM band. When operating inunlicensed radio frequency spectrum bands, wireless devices such as basestations 105 and UEs 115 may employ listen-before-talk (LBT) proceduresto ensure a frequency channel is clear before transmitting data. In somecases, operations in unlicensed bands may be based on a carrieraggregation configuration in conjunction with component carriersoperating in a licensed band (e.g., LAA). Operations in unlicensedspectrum may include downlink transmissions, uplink transmissions,peer-to-peer transmissions, or a combination of these. Duplexing inunlicensed spectrum may be based on frequency division duplexing (FDD),time division duplexing (TDD), or a combination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving device is equipped with one or moreantennas. MIMO communications may employ multipath signal propagation toincrease the spectral efficiency by transmitting or receiving multiplesignals via different spatial layers, which may be referred to asspatial multiplexing. The multiple signals may, for example, betransmitted by the transmitting device via different antennas ordifferent combinations of antennas. Likewise, the multiple signals maybe received by the receiving device via different antennas or differentcombinations of antennas. Each of the multiple signals may be referredto as a separate spatial stream and may carry bits associated with thesame data stream (e.g., the same codeword) or different data streams.Different spatial layers may be associated with different antenna portsused for channel measurement and reporting. MIMO techniques includesingle-user MIMO (SU-MIMO) where multiple spatial layers are transmittedto the same receiving device, and multiple-user MIMO (MU-MIMO) wheremultiple spatial layers are transmitted to multiple devices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g., synchronizationsignals, reference signals, beam selection signals, or other controlsignals) may be transmitted by a base station 105 multiple times indifferent directions, which may include a signal being transmittedaccording to different beamforming weight sets associated with differentdirections of transmission. Transmissions in different beam directionsmay be used to identify (e.g., by the base station 105 or a receivingdevice, such as a UE 115) a beam direction for subsequent transmissionand/or reception by the base station 105.

Some signals, such as data signals associated with a particularreceiving device, may be transmitted by a base station 105 in a singlebeam direction (e.g., a direction associated with the receiving device,such as a UE 115). In some examples, the beam direction associated withtransmissions along a single beam direction may be determined based atleast in in part on a signal that was transmitted in different beamdirections. For example, a UE 115 may receive one or more of the signalstransmitted by the base station 105 in different directions, and the UE115 may report to the base station 105 an indication of the signal itreceived with a highest signal quality, or an otherwise acceptablesignal quality. Although these techniques are described with referenceto signals transmitted in one or more directions by a base station 105,a UE 115 may employ similar techniques for transmitting signals multipletimes in different directions (e.g., for identifying a beam directionfor subsequent transmission or reception by the UE 115), or transmittinga signal in a single direction (e.g., for transmitting data to areceiving device).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a plurality of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a plurality of antenna elements of anantenna array, any of which may be referred to as “listening” accordingto different receive beams or receive directions. In some examples, areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based listeningaccording to different receive beam directions (e.g., a beam directiondetermined to have a highest signal strength, highest signal-to-noiseratio, or otherwise acceptable signal quality based listening accordingto multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer mayperform packet segmentation and reassembly to communicate over logicalchannels. A Medium Access Control (MAC) layer may perform priorityhandling and multiplexing of logical channels into transport channels.The MAC layer may also use HARQ to provide retransmission at the MAClayer to improve link efficiency. In the control plane, the RadioResource Control (RRC) protocol layer may provide establishment,configuration, and maintenance of an RRC connection between a UE 115 anda base station 105 or core network 130 supporting radio bearers for userplane data. At the Physical layer, transport channels may be mapped tophysical channels.

In some cases, UEs 115 and base stations 105 may support retransmissionsof data to increase the likelihood that data is received successfully.HARQ feedback is one technique of increasing the likelihood that data isreceived correctly over a communication link 125. HARQ may include acombination of error detection (e.g., using a cyclic redundancy check(CRC)), forward error correction (FEC), and retransmission (e.g.,automatic repeat request (ARQ)). HARQ may improve throughput at the MAClayer in poor radio conditions (e.g., signal-to-noise conditions). Insome cases, a wireless device may support same-slot HARQ feedback, wherethe device may provide HARQ feedback in a specific slot for datareceived in a previous symbol in the slot. In other cases, the devicemay provide HARQ feedback in a subsequent slot, or according to someother time interval.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period ofT_(s)=1/30,720,000 seconds. Time intervals of a communications resourcemay be organized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100 andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an evolved universal mobiletelecommunication system terrestrial radio access (E-UTRA) absoluteradio frequency channel number (EARFCN)) and may be positioned accordingto a channel raster for discovery by UEs 115. Carriers may be downlinkor uplink (e.g., in an FDD mode), or be configured to carry downlink anduplink communications (e.g., in a TDD mode). In some examples, signalwaveforms transmitted over a carrier may be made up of multiplesub-carriers (e.g., using multi-carrier modulation (MCM) techniques suchas orthogonal frequency division multiplexing (OFDM) or discrete Fouriertransform spread OFDM (DFT-S-OFDM)).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR).For example, communications over a carrier may be organized according toTTIs or slots, each of which may include user data as well as controlinformation or signaling to support decoding the user data. A carriermay also include dedicated acquisition signaling (e.g., synchronizationsignals or system information, etc.) and control signaling thatcoordinates operation for the carrier. In some examples (e.g., in acarrier aggregation configuration), a carrier may also have acquisitionsignaling or control signaling that coordinates operations for othercarriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples, the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

Devices of the wireless communications system 100 (e.g., base stations105 or UEs 115) may have a hardware configuration that supportscommunications over a particular carrier bandwidth or may beconfigurable to support communications over one of a set of carrierbandwidths. In some examples, the wireless communications system 100 mayinclude base stations 105 and/or UEs 115 that support simultaneouscommunications via carriers associated with more than one differentcarrier bandwidth.

Wireless communications system 100 may support communication with a UE115 on multiple cells or carriers, a feature which may be referred to ascarrier aggregation or multi-carrier operation. A UE 115 may beconfigured with multiple downlink component carriers and one or moreuplink component carriers according to a carrier aggregationconfiguration. Carrier aggregation may be used with both FDD and TDDcomponent carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation configuration or a dual connectivity configuration (e.g.,when multiple serving cells have a suboptimal or non-ideal backhaullink). An eCC may also be configured for use in unlicensed spectrum orshared spectrum (e.g., where more than one operator is allowed to usethe spectrum). An eCC characterized by wide carrier bandwidth mayinclude one or more segments that may be utilized by UEs 115 that arenot capable of monitoring the whole carrier bandwidth or are otherwiseconfigured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than othercomponent carriers, which may include use of a reduced symbol durationas compared with symbol durations of the other component carriers. Ashorter symbol duration may be associated with increased spacing betweenadjacent subcarriers. A device, such as a UE 115 or base station 105,utilizing eCCs may transmit wideband signals (e.g., according tofrequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc.) atreduced symbol durations (e.g., 16.67 microseconds). A TTI in eCC mayconsist of one or multiple symbol periods. In some cases, the TTIduration (that is, the number of symbol periods in a TTI) may bevariable.

Wireless communications system 100 may be an NR system that may utilizeany combination of licensed, shared, and unlicensed spectrum bands,among others. The flexibility of eCC symbol duration and subcarrierspacing may allow for the use of eCC across multiple spectrums. In someexamples, NR shared spectrum may increase spectrum utilization andspectral efficiency, specifically through dynamic vertical (e.g., acrossthe frequency domain) and horizontal (e.g., across the time domain)sharing of resources.

In a V2X communications system, sidelink communications 140 (e.g.,control or data transmissions) between UEs 115 may occur while one orboth UEs 115 are moving. For example, UE 115 within a V2X system may betraveling at a velocity and may attempt to transmit or receivecommunications with a neighboring UE 115 (e.g., via sidelinktransmission) traveling at a different velocity. In some cases, thedifference in the UE's 115 velocities may span a wide range (e.g., a fewkmph to about 500 kmph). This wide range of relative speed between theUEs 115 may make control information transmissions inefficient becauseefficient transmission of reference signals (e.g., DMRS) may vary basedon the relative speed between the UEs 115. For instance, when relativespeed between the UEs 115 is high, more reference signals in time may beutilized to ensure data is properly received (e.g., a higher density ofreference signals may be present). However, when relative speed betweenthe UEs 115 is low, fewer reference signals may need to be transmittedthan at higher relative speeds. As such, a UE 115 may employ enhancedDMRS design to ensure efficient spectral use and improve sidelinkperformance.

An adaptive design of DMRS time density based on UE 115 velocity mayallow for an increase in DMRS density in sidelink communications 140when relative speed is high and a decrease in DMRS density when relativespeed is low. The DMRS design may include a number of different DMRSpatterns of varying density corresponding to different speed ranges(e.g., two, three, or four DMRS patterns and corresponding speedranges), which will be discussed below in greater detail. In someexamples, a UE 115 may send assistance information (e.g., UE's 115speed, direction, location, relative speed, subcarrier spacing, and/orDMRS pattern index) to the transmitting UE 115 to help identify anefficient DMRS pattern based on the relative speed between the two UEs115. The transmitter may then transmit the DMRS and data via sidelinkcommunications 140 after the transmitter determines the DMRS pattern.Assistance information may be transmitted periodically, after a changeof assistance information, or based on a trigger from a transmitter.

In another example, a UE 115 may be unable to send or receive assistanceinformation (e.g., UE's 115 speed, direction, location, relative speed,subcarrier spacing, and/or DMRS pattern index). Thus, the transmittingUE 115 may determine the DMRS pattern based on its speed and/or thesubcarrier spacing without information of the receiver's speed (e.g., ina broadcast system). The transmitter may then indicate the selected DMRSpattern in control information via sidelink communications 140 to thereceiver followed by a transmission of the DMRS and data sidelinkcommunications 140. In some cases, the UEs 115 may follow a sidelinkschedule for sidelink communications 140 determined by a base station105 (e.g., when UEs 115 are operating in mode 1). For instance, one orboth of UEs 115 may send assistance information (e.g., UE's 115 speed,direction, location, relative speed, and/or DMRS pattern index) to thebase station 105 (e.g., gNB). The base station 105 may determine theDMRS pattern to be used by the transmitting UE 115 based on the receivedassistance information and then indicate the DMRS pattern to thetransmitting UE 115 via link 125. The transmitting UE 115 may thentransmit the DMRS, using the indicated pattern, and data using sidelinkcommunications 140.

In another example, a transmitting UE 115 may determine the DMRS patternto use with the receiving UE 115 based on HARQ feedback from thereceiving UE 115. The HARQ feedback may help determine a DMRS pattern byidentifying an error (e.g., BLER or packed error) that may be comparedto a threshold to determine the DMRS pattern for subsequenttransmissions on sidelink communications 140. For example, if the BLERis above a threshold, a denser DMRS pattern may be used for the nexttransmission in comparison to the previous transmission. Additionally oralternatively, a NACK may be used to determine received power at thetransmitting UE 115, and the received power may be compared to athreshold to determine the DMRS pattern for subsequent transmissions onsidelink communications 140. For instance, if the received power isabove a threshold, a denser DMRS pattern may be used for the nexttransmission in comparison to the previous transmission. Thetransmitting UE 115 may then transmit the DMRS and data via sidelinkcommunications 140 after the transmitting UE 115 determines the DMRSpattern. In some cases, the HARQ feedback may be stored over time suchthat the error rate or received power for UE 115 may be tracked overtime.

UE 115 may determine the DMRS pattern index using a mappingconfiguration. The mapping configuration may indicate a mapping betweena DMRS pattern and a corresponding relative speed range or feedbackthresholds. The mapping may be predefined (e.g., a table is stored at UE115), preconfigured (e.g., multiple tables may be stored at UE 115 wherea mapping in the table may be preconfigured, or multiple tables may bespecified, where one of the tables may be preconfigured for use), orconfigured by higher layer signaling (e.g., RRC signaling).

UEs 115 may include a reference signal manager 101, which may enable aUE 115 to identify a mapping configuration to use for determining DMRSpatterns for relative speed ranges. The UE 115 may transmit or receiveassistance information to determine the DMRS pattern for currentoperating conditions of UE 115. In some examples, the UE 115 maytransmit data including the DMRS pattern, for example, in a sidelinkcommunication 140 to another UE 115. In some examples, the referencesignal manager 101 may transmit assistance information to a secondwireless device, the assistance information associated with a speed ofthe first wireless device, or a location of the first wireless device,or a combination thereof and identify a reference signal pattern of areference signal for demodulating data, the reference signal patternbased on the assistance information. In some cases, the reference signalmanager 101 may also determine a speed of the first wireless device,identify a subcarrier spacing for communicating with one or more otherwireless devices, determine, based on the speed of the first wirelessdevice and the subcarrier spacing, a reference signal pattern of areference signal for demodulating data, and transmit the data and thereference signal to the one or more other wireless devices, thereference signal being transmitted in accordance with the referencesignal pattern.

Additionally or alternatively, the reference signal manager 101 may alsotransmit assistance information to a base station, the assistanceinformation associated with a speed of the first wireless device, or alocation of the first wireless device, or a combination thereof,receive, from the base station, an indication of a reference signalpattern of a reference signal for demodulating data, the referencesignal pattern being based on the assistance information, and transmitthe data and the reference signal to a second wireless device, thereference signal being transmitted in accordance with the referencesignal pattern. The reference signal manager 101 may receive, from oneor more other wireless devices, feedback information in response to oneor more previous data transmissions to the one or more other wirelessdevices, determine a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information, and transmit the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

FIG. 2 illustrates an example of a wireless communications system 200that supports reference signal patterns based on relative speed betweena transmitter and receiver in accordance with one or more aspects of thepresent disclosure. In some examples, wireless communications system 200may implement aspects of wireless communications system 100. In someexamples, the wireless communications system 200 may include UEs 115-aand 115-b, and base station 105-a which may be examples of a UE 115 andbase station 105, respectively, described with reference to FIG. 1 . Itis noted that communications between two UEs 115 are illustrated inwireless communications system 200 for the sake of brevity, and thetechniques described herein may be applicable to multiple UEs 115 withina system. For instance, UE 115-a may communicate with multiple UEs 115,for example, using broadcast or groupcast communications schemes.

In some cases, the UEs 115-a and 115-b may communicate with each otherwithin a V2X system (e.g., using the sidelink communications 205) andmay employ a flexible DMRS pattern design to enable efficient sidelinkcommunications. For example, efficient transmissions of referencesignals (e.g., DMRS) may vary based on the relative speed between UEs115-a and 115-b. As described herein, the adaptive time density of DMRSbased on UE 115-a or 115-b velocity may allow for an increase in DMRSdensity when relative speed between UEs 115-a and 115-b is high and adecrease in DMRS density when relative speed between UEs 115-a and 115-bis low. Further, system 200 may be divided into geographical zones(e.g., zone 215 and 220), shown by the dotted lines.

According to some aspects, the DMRS design may include a number ofdifferent DMRS patterns of varying density corresponding to differentspeed categories (e.g., two, three, or four DMRS patterns andcorresponding speed ranges) to be used for data channel estimation. Forinstance, UE 115-a may attempt to decode sidelink communications 205(e.g., data transmissions) from the UE 115-b when one or both of UEs115-a and 115-b are in motion. For example, UE 115-b within wirelesscommunications system 200 may be traveling at a relatively low speed(e.g., 10 kmph in a direction) to point 210 and may attempt to transmitor receive communications with a stationary neighboring UE 115-a (e.g.,via sidelink transmission 205). Assistance information (e.g., a speed,direction, location (e.g., zone ID), relative speed, subcarrier spacing,and/or DMRS pattern index of a UE 115) from one or both UEs 115-a and115-b may be used to determine the relative speed between UEs 115-a and115-b. In some cases, the difference in the velocities of the UEs 115(e.g., relative speed between one another) may be categorized (e.g.,mapped) into a speed category (e.g., low: 0-60 kmph, medium: 61-120kmph, or high: greater than 120 kmph), where a different DMRS patternmay correspond to each speed category (e.g., low, medium, and high).Example DMRS patterns are shown in FIG. 3 and described in greaterdetail herein. The variable DMRS design (e.g., use of assistanceinformation) may vary based on the system's 200 configurations (e.g.,unicast, groupcast, or broadcast).

In some examples, UE 115-a may send assistance information (e.g., UE's115-a speed, direction, location (e.g., zone ID), relative speed,subcarrier spacing, and/or DMRS pattern index) to the transmitting UE115-b to help identify an efficient DMRS pattern based on the relativespeed between the two UEs 115-a and 115-b. In some examples, assistanceinformation may be transmitted in sidelink channel information (SCI), asidelink data channel (SL-SCH) (e.g., MAC control element (CE)), or afeedback channel. In some cases, relative speed and/or a DMRS patternindex may be determined at UE 115-a when UE 115-a has assistanceinformation about UE 115-b. The transmitting UE 115-b may then transmitthe DMRS and data after the transmitting UE 115-b determines the DMRSpattern based on the assistance information. Assistance information maybe transmitted periodically (e.g., according to a schedule), after achange of assistance information (e.g., change in speed and/or directionof UE 115-a or 115-b), or based on a trigger from a transmitting UE115-b. This example is described in greater detail in FIG. 4 .

In another example, UE 115-b may operate in a broadcast configurationand may not receive transmissions from the receiver UE 115-a.Accordingly, UE 115-b may be unable to receive assistance information(e.g., UE's speed, direction, location, relative speed, subcarrierspacing, and/or DMRS pattern index) from UE 115-a. Thus, thetransmitting UE 115-b may determine the DMRS pattern based on its speedwithout information of the receiving UE's 115-a speed. The transmittingUE 115-b may then indicate the selected DMRS pattern in controlinformation via sidelink 205 to the receiving UE 115-a followed by atransmission of the DMRS and data via sidelink 205. This example isdescribed in greater detail in FIG. 5 .

In some cases, the UEs 115-a and 115-b may utilize resources (e.g., oversidelink 205) scheduled by base station 105-a (e.g., when operating inmode 1 of a sidelink communications scheme). In such cases, one or bothof UEs 115-a and 115-b may send assistance information (e.g., UE's ownspeed, direction, location, relative speed, and/or DMRS pattern index)to the base station 105-a (e.g., gNB) via links 225. In some examples,assistance information may be transmitted in uplink channel information(UCI), a data channel (PUSCH) (e.g., MAC control element (CE)), or afeedback channel. The base station 105-a may then determine the DMRSpattern to be used by the transmitting UE 115-a based on the receivedassistance information and then indicate the DMRS pattern to thetransmitting UE 115-a via link 225. The transmitting UE 115-a may thentransmit the DMRS, using the indicated pattern, and data to thereceiving UE 115-b via sidelink 205. This example is described ingreater detail in FIG. 6 .

In another example, a transmitting UE 115-a may determine the DMRSpattern to use with the receiving UE 115-b based on HARQ feedback fromthe receiving UE 115-b. The HARQ feedback may help determine a DMRSpattern by identifying an error (e.g., BLER or packed error) that may becompared to a threshold to determine the DMRS pattern for subsequenttransmissions via sidelink 205 (e.g., in a unicast configuration). Forexample, if the BLER satisfies a threshold, a denser DMRS pattern may beused for the next transmission via sidelink 205 in comparison to theprevious transmission via sidelink 205. Additionally or alternatively, anegative acknowledgement (NACK) may be used to determine received powerat the transmitting UE 115-a, and the received power may be compared toa threshold to determine the DMRS pattern for subsequent transmissionsvia sidelink 205 (e.g., in a groupcast configuration). For instance, ifthe received power is above a threshold, a denser DMRS pattern may beused for the next transmission via sidelink 205 in comparison to theprevious transmission via sidelink 205. For example, in a groupcastdeployment, multiple UEs 115 may fail in decoding and send feedbackinformation (e.g., NACK) to the transmitting UE 115-a. In cases, wherethe transmitting UE 115-a receives a larger NACK received signal power(e.g., because NACK signals may be combined over the air), thetransmitting UE 115-a may determine that a denser DMRS pattern may beused (e.g., as compared to the DMRS pattern used for the previoustransmission). The transmitting UE 115-a may then transmit the DMRS anddata via sidelink 205 after the transmitting UE 115-a determines theDMRS pattern. In some cases, the HARQ feedback may be stored over timesuch that the error rate or received power for a UE may be tracked overtime. This example is described in greater detail in FIG. 7 .

The UEs 115-a and 115-b, and base station 105-a may determine the DMRSpattern index using a mapping configuration. The mapping configurationmay indicate a one-to-one mapping between a DMRS pattern and acorresponding relative speed range or feedback thresholds. For example,two speed categories and DMRS patterns may be configured, such as a lowspeed category (e.g., 0 to 120 kmph) may correspond to a low densityDMRS pattern, while a high speed category (e.g., greater than 120 kmph)may correspond to a high density DMRS pattern. The mapping may bepredefined (e.g., a table is stored at the UEs 115-a and 115-b),preconfigured (multiple tables may be stored at the UEs 115-a and115-b), or configured by higher layer signaling (e.g., RRC signalingfrom base station 105-a).

In some examples, a DMRS pattern may be determined for more than one UE115 when the system is operating in a broadcast or groupcastconfiguration. Each receiving UE 115 may be moving at different speed,but one DMRS pattern may be used for all UEs 115. The DMRS pattern maybe based on assistance information from one or more UEs 115 and mayaccount for the different conditions of each sidelink 205 with each UE115. For instance, a DMRS pattern may be selected based on the worstsidelink 205 (e.g., highest relative speed between UEs 115). Forexample, the DMRS pattern with the highest DMRS time density ofindicated DMRS patterns from receiving UEs 115 may be selected.

Alternatively, a DMRS pattern may be selected based on the worstsidelink 205 and a BLER target. For example, the DMRS pattern may beselected within an error tolerance (e.g., 5% or 15%) such that not everyreceiving UE 115 is ensured successful decoding of the data channel. Forexample, transmitting UE 115 receives assistance info from 30 receivingUEs 115 and determines the relative speed for the 30 links based onthree speed categories: low, medium, and high. 28 of the links withinthe low to medium relative speed categories, and 2 within the highrelative speed category. If the BLER target is 0.1 (i.e., tolerance to10% error), then the DMRS pattern may be selected based on the mediumspeed category. Therefore, the two UEs 115 within the high speedcategory may not decode correctly, but the BLER target can still be met.

The DMRS pattern may be based on subcarrier spacing since a largersubcarrier spacing may correspond to a smaller (e.g., shorter) OFDMsymbol duration, and a DMRS pattern that works for larger subcarrierspacing may not work for smaller subcarrier spacing because a smallersubcarrier spacing may need a denser DMRS pattern than larger subcarrierspacing, even within the same or similar relative speeds. For example,when the transmitting UE 115 is transmitting with 30 kHz subcarrierspacing, a pattern with DMRS in three symbols (e.g., as described hereinand shown in FIG. 3D) may be determined (medium speed category) for arelative speed of 100 kmph. However, when the transmitting UE 115 istransmitting with 15 kHz subcarrier spacing, a reference signal patternwith DMRS in six symbols (e.g., as described herein and as shown in FIG.3E) may be determined (high speed category) for a relative speed of 100kmph (e.g., due to a relatively longer duration of a slot). In anotherexample, when the transmitting UE 115 is transmitting with 60 kHzsubcarrier spacing, the pattern with DMRS in two symbols (e.g., asdescribed herein and as shown in FIG. 3C) may be determined (low speedcategory) for a relative speed of 100 kmph (e.g., due to a relativelyshorter duration of a slot).

FIGS. 3A through 3E illustrate an example of reference signal patterns300 that support reference signal patterns based on relative speedbetween a transmitter and receiver in accordance with one or moreaspects of the present disclosure. In some examples, the DMRS patterns300-a through 300-e may implement aspects of wireless communicationssystems 100 or 200 or may be implemented by a UE 115 such as a vehicle(or other wireless device in a V2X system), as described herein.

As shown in FIG. 3A, the reference signal pattern 300-a (e.g., a DMRSpattern) may include OFDM symbols 305 with DMRS 310 or without DMRS 310.For example, symbol 315 may be an example of an OFDM symbol 305 withoutDMRS 310, and symbol 320 may be an example of an OFDM symbol 305 withDMRS 310. In some examples, a symbol 320 with DMRS 310 may betransmitted every seventh symbol, such that there are six symbols 315without DMRS 310 between each symbol 320 with DMRS 310. In some cases,more symbols 315 without DMRS 310 may be present between each symbol 320with DMRS 310 (e.g., as compared to other DMRS patterns 300).

As shown in FIG. 3B, the reference signal pattern 300-b may include OFDMsymbols 305 with DMRS 310 or without DMRS 310. For example, symbol 315may be an example of a symbol 305 without DMRS 310, and symbol 320 maybe an example of a symbol 305 with DMRS 310. In some examples, a symbol320 with DMRS 310 may be transmitted every third or fourth symbol suchthat there are two or three symbols 315 without DMRS 310 between eachsymbol 320 with DMRS 310, respectively.

In some examples, the reference signal patterns 300-a and 300-b may beused when two speed categories are used. For instance, a low speedcategory (e.g., 0 to 100 kmph) may correspond to DMRS pattern 300-a,while a high speed category (e.g., greater than 100 kmph) may correspondto DMRS pattern 300-b. This example does not limit the number ofcategories to two, and more or less categories and corresponding DMRSpatterns may be used. For example, three categories are described withreference to FIGS. 3C-3E. In some examples, the mapping described herecorresponds to a specific subcarrier spacing, for example, for 30 kHzsubcarrier spacing. When subcarrier spacing is different is different,the mapping is different. For example, when subcarrier spacing is 60kHz, pattern 300-b corresponds to a high speed category (e.g., greaterthan 200 kmph).

As shown in FIG. 3C, the reference signal pattern 300-c may include OFDMsymbols 305 with DMRS 310 or without DMRS 310. For example, symbol 315may be an example of a symbol 305 without DMRS 310, and symbol 320 maybe an example of a symbol 305 with DMRS 310. In some examples, a symbol320 with DMRS 310 may be transmitted every tenth symbol such that thereare nine symbols 315 without DMRS 310 between each symbol 320 with DMRS310, respectively.

As shown in FIG. 3D, the reference signal pattern 300-d may include OFDMsymbols 305 with DMRS 310 or without DMRS 310. For example, symbol 315may be an example of a symbol 305 without DMRS 310, and symbol 320 maybe an example of a symbol 305 with DMRS 310. In some examples, a symbol320 with DMRS 310 may be transmitted every fifth symbol such that thereare four symbols 315 without DMRS 310 between each symbol 320 with DMRS310, respectively.

As shown in FIG. 3E, the reference signal pattern 300-e may include OFDMsymbols 305 with DMRS 310 or without DMRS 310. For example, symbol 315may be an example of a symbol 305 without DMRS 310, and symbol 320 maybe an example of a symbol 305 with DMRS 310. In some examples, a symbol320 with DMRS 310 may be transmitted every other symbol such that thereis one symbol 315 without DMRS 310 between each symbol 320 with DMRS310, respectively. The DMRS pattern may last for one or more slots(e.g., fourteen symbols).

In some examples, the reference signal patterns 300-c, 300-d, and 300-emay be used when three speed categories are used. For instance, a lowspeed category (e.g., 0 to 60 kmph) may correspond to DMRS pattern300-c, while a medium speed category (e.g., 60 to 150 kmph) maycorrespond to DMRS pattern 300-d, and a high speed category (e.g.,greater than 150 kmph) may correspond to DMRS pattern 300-e. Thisexample does not limit the number of categories to three, and more orless categories and corresponding DMRS patterns may be used. Forexample, four speed categories may be used corresponding to DMRSpatterns 300-c, 300-a, 300-d, and 300-e, from lowest to highest speedcategories respectively. Additional categories or mapping may be usedfor different subcarrier spacing. For example, mapping may be based onspeed and/or subcarrier spacing, such that mapping may be different fromcategories containing only speed. For instance, the range of a speedcategory may be different when subcarrier spacing is considered or eachsubcarrier spacing may have a mapping table as an alternative or inaddition to the speed mapping tables.

FIG. 4 illustrates an example of a process flow 400 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. In some examples, process flow 400 may implement aspects ofwireless communications system 100. Process flow 400 may be implementedby a UE 115-c and UE 115-d, or any other examples of UEs 115 asdescribed herein. Alternative examples of the following may beimplemented, where some steps are performed in a different order thandescribed or are not performed at all. In some cases, steps may includeadditional features not mentioned below, or further steps may be added.

At 405, UE 115-c may optionally receive transmitter assistance (e.g.,UE's 115-d speed, direction, location (e.g., zone ID), relative speed,subcarrier spacing, and/or DMRS pattern index) information from UE115-d. The transmitter assistance information may be transmitted forother purposes than DMRS pattern design determination but may still beused by UE 115-c, which may reduce signal overhead between UE 115-c andUE 115-d by reducing the addition of DMRS pattern design specificassistance information.

In some examples, assistance information may be transmitted in SCI, asidelink data channel (SL-SCH) (e.g., MAC CE), or a feedback channel.Assistance information may be transmitted periodically (e.g., accordingto a predefined or preconfigured time period, indicated by RRCsignaling), after a change of assistance information (e.g., change inspeed, direction, location and/or relative speed of UE 115-c or 115-d),or based on a trigger from a receiving UE 115-c. More specifically, achange of assistance information at UE 115-d may include when the changeof speed exceeds a threshold (e.g., a change of absolute value is largerthan a threshold, or change from one speed category to another: low tomedium), a change of direction exceeds a threshold, the location ischanged (e.g., zone ID changed), the change of relative speed exceeds athreshold (if UE 115-d determines relative speed of UEs 115-c and115-d), and/or the determined DMRS pattern is changed (if UE 115-ddetermines DMRS pattern).

In some cases, speed may be indicated by an index mapped from absolutespeed. For example, three indices to indicate low, medium, and highspeed, and each of the three indices corresponds to a speed range (e.g.,low: less than or equal to 60 kmph, mid: greater than 60 and less thanor equal to 120 kmph, and high: greater than 120 kmph). In someexamples, direction may be indicated by an index mapped from UE's 115absolute direction. For instance, the degree from north direction,rounded to a finite set of directions (e.g., eight directions mappedfrom [0, 360) degrees, resulting in eight equal ranges of 45 degrees).

In some examples, speed and/or direction may be determined by a UE's 115location (e.g., zone ID) included in the assistance information. Forinstance, a UE 115 may know what zone it is in (e.g., zone 215 or zone220) where a zone is a geographical area with a corresponding zone ID.From the change rate of zones (e.g., zone IDs), a moving speed can bedetermined at UE 115-c or 115-d over time. For instance, the size ofeach zone may be known, and based on the location of a UE 115 indifferent zones over time, the speed of the UE 115 may be determined.

At 410, UE 115-c may optionally determine a relative speed betweenitself, UE 115-c, and UE 115-d. In some cases, this determination may bebased on the received transmitter assistance information. For example,if UE 115-c is in speed category low in a first direction, and UE 115-dis in speed category low in a second direction, and if the first andsecond directions are opposite, then the relative speed is determined aswithin the medium speed category if a three category system is used(e.g., FIGS. 3C through 3E).

At 415, UE 115-c may optionally determine a DMRS pattern andcorresponding index based on the determination of relative speed at 410.Example DMRS patterns are shown in FIGS. 3A-3E.

At 420, UE 115-c may transmit receiver assistance information to UE115-d, which may be similar to transmitter assistance information. Insome cases, this assistance information may include UE's 115-c speed,direction, location (e.g., zone ID), relative speed, subcarrier spacing,and/or DMRS pattern index. The assistance information may include a DMRSpattern index based on the determination of a DMRS pattern at 415. Insome examples, assistance information may be transmitted in SCI, asidelink data channel (SL-SCH) (e.g., MAC CE), or a feedback channel.Assistance information may be transmitted periodically (e.g., accordingto a schedule), after a change of assistance information (e.g., changein speed and/or direction of UE 115-a or 115-b), or based on a triggerfrom a transmitting UE 115-b. More specifically, a change of assistanceinformation at UE 115-c may include when the change of speed exceeds athreshold (e.g., a change of absolute value is larger than a threshold,or change from one speed category to another: low to medium), a changeof direction exceeds a threshold, the location is changed (e.g., zone IDchanged), the change of relative speed exceeds a threshold (if UE 115-cdetermines relative speed of UEs 115-c and 115-d), and/or the determinedDMRS pattern is changed (if UE 115-c determines DMRS pattern).

At 425, UE 115-d may optionally determine a relative speed betweenitself, UE 115-d, and UE 115-d. In some cases, this determination may bebased on the received receiver assistance information, as discussedabove in relation to the determination at 410. For example, if UE 115-cis in speed category medium in a first direction, and UE 115-d is inspeed category low in the same direction, then the relative speed isdetermined to be within the low speed category if a three categorysystem is used (e.g., FIGS. 3C through 3E).

At 430, UE 115-d may determine a DMRS pattern based on the receiverassistance information and optionally the determination or relativespeed at 425. Example DMRS patterns are shown in FIGS. 3A-3E. UE 115-dmay maintain record of UE's 115-c past assistance information, and UE115-d may redetermine a DMRS pattern when the assistance informationchanges. For example, UE 115-d may maintain ten receivers' speedinformation and determined the relative speeds for the ten sidelinks. UE115-d may determine a DMRS pattern based on the relative speeds of theten sidelinks, and UE 115-d continues using the DMRS pattern if norelative speed change (or the change is not large enough to trigger achange of DMRS pattern).

At 435, UE 115-d may transmit, to UE 115-c, using the DMRS patterndetermined at 430 along with data. In some cases, an indication of theDMRS pattern to be used at 435 may be sent to UE 115-c.

FIG. 5 illustrates an example of a process flow 500 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. In some examples, process flow 500 may implement aspects ofwireless communications system 100. Process flow 500 may be implementedby a UE 115-e and UE 115-f, or any other examples of UEs 115 asdescribed herein. Alternative examples of the following may beimplemented, where some steps are performed in a different order thandescribed or are not performed at all. In some cases, steps may includeadditional features not mentioned below, or further steps may be added.

At 505, a UE 115-f may determine the speed (and optionally direction) ofitself, UE 115-f UE 115-f may operate in a broadcast configuration andmay not receive transmissions from the receiver UE 115-e, and thus, UE115-f may not be able to receive assistance information from UE 115-e.In some examples, UE 115-e may be unable to transmit assistanceinformation to UE 115-f. In some cases, UE 115-f may assume UE 115-e isstationary or moving in the opposite direction at a similar speed as UE115-f.

At 510, the UE 115-f may determine a DMRS pattern for the sidelinkcommunications with UE 115-e based on the determined speed at 505.Example DMRS patterns are shown in FIGS. 3A-3E.

At 515, UE 115-f may transmit, to UE 115-e, using the DMRS patterndetermined at 510 along with data. In some cases, an indication of theDMRS pattern to be used at 510 may be sent to UE 115-e (e.g., via SCI).

FIG. 6 illustrates an example of a process flow 600 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. In some examples, process flow 600 may implement aspects ofwireless communications system 100. Process flow 600 may be implementedby UE 115-g, UE 115-e, base station 105-b, or any other examples of UEs115 or base stations 105 as described herein. Alternative examples ofthe following may be implemented, where some steps are performed in adifferent order than described or are not performed at all. In somecases, steps may include additional features not mentioned below, orfurther steps may be added.

At 602, UE 115-g may optionally transmit, to UE 115-h, sidelinkcommunications. For example, UE 115-g may transmit data to UE 115-h forV2X or V2V communications. In some cases, UEs 115-g and 115-h may beoperating in mode 1 such that base station 105-b assists in sidelinkscheduling.

At 605, UE 115-g may optionally transmit receiver assistance informationto base station 105-b. At 610, UE 115-h may transmit transmitterassistance information to base station 105-b. In some cases, one or bothof receiver and transmitter assistance information may be transmitted tobase station 105-b. In some cases, the assistance information mayinclude each respective UE's 115-g or 115-h speed, direction, location(e.g., zone ID), relative speed, subcarrier spacing, and/or DMRS patternindex. In some examples, assistance information may be transmitted inUCI, a data channel (e.g., PUSCH, MAC CE), or a feedback channel.

At 615, base station 105-b may determine a relative speed between UE115-g and UE 115-h. In some cases, this determination at 615 may bebased on the received assistance information (e.g., receiver and/ortransmitter assistance information), similar to the relative speeddeterminations in process flow 400.

At 620, base station 105-b may determine a DMRS pattern andcorresponding DMRS pattern index based on the determination of relativespeed at 615. At 625, base station 105-b may transmit, to UE 115-h, theDMRS pattern index based on the determination of a DMRS pattern at 620.Example DMRS patterns are shown in FIGS. 3A-3E.

At 630, UE 115-h may determine the DMRS pattern based on the receivedDMRS pattern index at 625 (e.g., based on the known mappingconfiguration). For example, two speed categories and DMRS patterns maybe configured, such as a low speed category (e.g., 0 to 120 kmph) maycorrespond to a low density DMRS pattern, while a high speed category(e.g., greater than 120 kmph) may correspond to a high density DMRSpattern. The mapping may be predefined (e.g., a table is stored at theUEs 115-g and 115-h), preconfigured (multiple tables may be stored atthe UEs 115-g and 115-h), or configured by higher layer signaling (e.g.,RRC signaling from base station 105-b).

At 635, UE 115-h may transmit, to UE 115-g, using the DMRS patterndetermined at 620 and 630 along with data. In some cases, an indicationof the DMRS pattern to be used at 635 may be sent to UE 115-g.

FIG. 7 illustrates an example of a process flow 700 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. In some examples, process flow 700 may implement aspects ofwireless communications system 100. Process flow 700 may be implementedby a UE 115-i and UE 115-j, or any other examples of UEs 115 asdescribed herein. Alternative examples of the following may beimplemented, where some steps are performed in a different order thandescribed or are not performed at all. In some cases, steps may includeadditional features not mentioned below, or further steps may be added.

At 705, UE 115-i may receive a sidelink communication (e.g., datatransmission) from UE 115-j. At 710, UE 115-i may transmit, to UE 115-j,HARQ feedback (e.g., acknowledgment (ACK) or NACK) for the sidelinkcommunication received at 705.

At 715, UE 115-j may optionally determine an error based on the receivedHARQ feedback. In some cases, this error determination may be comparedto a threshold and tracked over time, and UE 115-j may reselect a DMRSpattern when the error rate has changed. For example, UE 115-j maycompute the BLER or packet error from HARQ feedback 710 over a timeperiod, and if the BLER is higher than a target, the UE 115-j maydetermine that a DMRS pattern with denser DMRS symbol locations shouldbe used in subsequent sidelink communications. Error determinations mayapply to unicast configurations.

At 720, UE 115-j may optionally determine received power of the HARQfeedback (e.g., NACK when in a groupcast configuration with SFNfeedback). In groupcast, only NACK(s) may be received by UE 115-j. Insome cases, this received power may be compared to a threshold andtracked over time, and UE 115-j may reselect a DMRS pattern when thereceived power has changed. For example, UE 115-j may measure thereceived power of a NACK signal in HARQ feedback 710, and if the poweris higher than a threshold, the UE 115-j may determine that a DMRSpattern with denser DMRS symbol locations should be used in subsequentsidelink communications. The received power measurement may be aone-shot measurement or measurement over multiple NACK receptions.

At 725, UE 115-j may determine (or redetermine) a DMRS pattern based onone or both of the comparisons of error and received power with theirrespective thresholds.

At 730, UE 115-j may transmit, to UE 115-i, using the DMRS patterndetermined at 725 along with data. In some cases, an indication of theDMRS pattern to be used at 730 may be sent to UE 115-i.

FIG. 8 shows a block diagram 800 of a device 805 that supports referencesignal patterns based on relative speed between a transmitter andreceiver in accordance with one or more aspects of the presentdisclosure. The device 805 may be an example of aspects of a UE 115 asdescribed herein. The device 805 may include a receiver 810, a referencesignal manager 815, and a transmitter 820. The device 805 may alsoinclude a processor. Each of these components may be in communicationwith one another (e.g., via one or more buses).

The receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal patterns based on relative speed between a transmitter andreceiver, etc.). Information may be passed on to other components of thedevice 805. The receiver 810 may be an example of aspects of thetransceiver 1120 described with reference to FIG. 11 . The receiver 810may utilize a single antenna or a set of antennas.

The reference signal manager 815 may transmit assistance information toa second wireless device, the assistance information associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof and determine an adaptive referencesignal pattern of a reference signal for demodulating data, the adaptivereference signal pattern based on the assistance information. Thereference signal manager 815 may also determine a speed of the firstwireless device, identify a subcarrier spacing for communicating withone or more other wireless devices, determine, based on the speed of thefirst wireless device and the subcarrier spacing, a reference signalpattern of a reference signal for demodulating data, and transmit thedata and the reference signal to the one or more other wireless devices,the reference signal being transmitted in accordance with the referencesignal pattern. The reference signal manager 815 may also transmitassistance information to a base station, the assistance informationassociated with a speed of the first wireless device, or a location ofthe first wireless device, or a combination thereof, receive, from thebase station, an indication of a reference signal pattern of a referencesignal for demodulating data, the reference signal pattern being basedon the assistance information, and transmit the data and the referencesignal to a second wireless device, the reference signal beingtransmitted in accordance with the reference signal pattern. Thereference signal manager 815 may also receive, from one or more otherwireless devices, feedback information in response to one or moreprevious data transmissions to the one or more other wireless devices,determine a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information, and transmit the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern. Thereference signal manager 815 may be an example of aspects of thereference signal manager 1110 described herein.

The actions performed by the reference signal manager 815 as describedherein may be implemented to realize one or more potential advantages.One implementation may allow a UE 115 to save power and increase batterylife by avoiding unsuccessful reception or transmission ofcommunications when traveling at different speeds by optimizing the DMRSdensity for the current speed of the UE. Additionally or alternatively,the UE 115 may further reduce signaling overhead by reducing the DMRSdensity at slow speeds when dense DMRS is not needed for successfulcommunications. Another implementation may provide improved quality andreliability of service at the UE 115, as latency and the number ofseparate resources allocated to the UE 115 may be optimized based on theDMRS density, which may be based on the speed or location of UE 115.

The reference signal manager 815, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the reference signal manager 815, orits sub-components may be executed by a general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The reference signal manager 815, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, thereference signal manager 815, or its sub-components, may be a separateand distinct component in accordance with various aspects of the presentdisclosure. In some examples, the reference signal manager 815, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 820 may transmit signals generated by other componentsof the device 805. In some examples, the transmitter 820 may becollocated with a receiver 810 in a transceiver module. For example, thetransmitter 820 may be an example of aspects of the transceiver 1120described with reference to FIG. 11 . The transmitter 820 may utilize asingle antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 that supports referencesignal patterns based on relative speed between a transmitter andreceiver in accordance with one or more aspects of the presentdisclosure. The device 905 may be an example of aspects of a device 805,or a UE 115 as described herein. The device 905 may include a receiver910, a reference signal manager 915, and a transmitter 950. The device905 may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to referencesignal patterns based on relative speed between a transmitter andreceiver, etc.). Information may be passed on to other components of thedevice 905. The receiver 910 may be an example of aspects of thetransceiver 1120 described with reference to FIG. 11 . The receiver 910may utilize a single antenna or a set of antennas.

The reference signal manager 915 may be an example of aspects of thereference signal manager 815 as described herein. The reference signalmanager 915 may include a mobility manager 920, a reference signalpattern manager 925, a speed component 930, a subcarrier spacingcomponent 935, a communications manager 940, and a feedback component945. The reference signal manager 915 may be an example of aspects ofthe reference signal manager 1110 described herein.

The mobility manager 920 may transmit assistance information to a secondwireless device, the assistance information associated with a speed ofthe first wireless device, or a location of the first wireless device,or a combination thereof.

The reference signal pattern manager 925 may determine an adaptivereference signal pattern of a reference signal for demodulating data,the adaptive reference signal pattern based on the assistanceinformation. The speed component 930 may determine a speed of the firstwireless device. The subcarrier spacing component 935 may identify asubcarrier spacing for communicating with one or more other wirelessdevices.

The reference signal pattern manager 925 may determine, based on thespeed of the first wireless device and the subcarrier spacing, areference signal pattern of a reference signal for demodulating data.The communications manager 940 may transmit the data and the referencesignal to the one or more other wireless devices, the reference signalbeing transmitted in accordance with the reference signal pattern.

The mobility manager 920 may transmit assistance information to a basestation, the assistance information associated with a speed of the firstwireless device, or a location of the first wireless device, or acombination thereof. The reference signal pattern manager 925 mayreceive, from the base station, an indication of a reference signalpattern of a reference signal for demodulating data, the referencesignal pattern being based on the assistance information.

The communications manager 940 may transmit the data and the referencesignal to a second wireless device, the reference signal beingtransmitted in accordance with the reference signal pattern. Thefeedback component 945 may receive, from one or more other wirelessdevices, feedback information in response to one or more previous datatransmissions to the one or more other wireless devices.

The reference signal pattern manager 925 may determine a referencesignal pattern of a reference signal for demodulating data, thereference signal pattern being based on the feedback information. Thecommunications manager 940 may transmit the data and the referencesignal to the one or more other wireless devices, the reference signalbeing transmitted in accordance with the reference signal pattern.

The transmitter 950 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 950 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 950 may be an example of aspects of the transceiver 1120described with reference to FIG. 11 . The transmitter 950 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a reference signal manager 1005that supports reference signal patterns based on relative speed betweena transmitter and receiver in accordance with one or more aspects of thepresent disclosure. The reference signal manager 1005 may be an exampleof aspects of a reference signal manager 815, a reference signal manager915, or a reference signal manager 1110 described herein. The referencesignal manager 1005 may include a mobility manager 1010, a referencesignal pattern manager 1015, a speed component 1020, a directioncomponent 1025, a location component 1030, a relative speed manager1035, a communications manager 1040, a subcarrier spacing component1045, memory 1050, and a feedback component 1055. Each of these modulesmay communicate, directly or indirectly, with one another (e.g., via oneor more buses).

The mobility manager 1010 may transmit assistance information to asecond wireless device, the assistance information associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof.

In some examples, the mobility manager 1010 may transmit assistanceinformation to a base station, the assistance information associatedwith a speed of the first wireless device, or a location of the firstwireless device, or a combination thereof. In some examples, themobility manager 1010 may transmit, as part of the assistanceinformation, a speed value indicating the speed of the first wirelessdevice. In some examples, the mobility manager 1010 may transmit, aspart of the assistance information, a direction value indicating themovement direction of the first wireless device.

In some examples, the mobility manager 1010 may transmit, as part of theassistance information, a location value indicating the location of thefirst wireless device. In some examples, the mobility manager 1010 maydetermine a velocity of the first wireless device. In some examples, themobility manager 1010 may transmit, as part of the assistanceinformation, an indication of the relative speed.

In some examples, the mobility manager 1010 may transmit, as part of theassistance information, an indication of the reference signal pattern.In some examples, the mobility manager 1010 may identify a highestrelative speed from the relative speeds of the set of communicationlinks, where the reference signal pattern is based on the highestrelative speed.

In some examples, the mobility manager 1010 may receive first assistanceinformation and second assistance information from the second wirelessdevice, each of the first assistance information and the secondassistance information being associated with a respective speed of thesecond wireless device, or a respective location of the second wirelessdevice, or a combination thereof. In some examples, the mobility manager1010 may identify a periodicity for transmitting the assistanceinformation, where the assistance information is transmitted inaccordance with the periodicity.

In some examples, the mobility manager 1010 may generate firstassistance information and second assistance information for the firstwireless device, each of the first assistance information and the secondassistance information being associated with a respective speed of thefirst wireless device, or a respective location of the first wirelessdevice, or a combination thereof.

In some examples, the mobility manager 1010 may identify a differencebetween the first assistance information and the second assistanceinformation. In some examples, the mobility manager 1010 may transmitthe assistance information based on identifying the difference. In someexamples, the mobility manager 1010 may receive a request to transmitthe assistance information, where the assistance information istransmitted in response to the received request.

In some examples, the mobility manager 1010 may transmit the assistanceinformation as part of sidelink control information, or as part of amedium access control (MAC) control element, or over a sidelink datachannel, or over a sidelink shared channel, or over a feedback channel,or a combination thereof. The reference signal pattern manager 1015 mayidentify a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern based on the assistanceinformation.

In some examples, the reference signal pattern manager 1015 maydetermine, based on the speed of the first wireless device and thesubcarrier spacing, a reference signal pattern of a reference signal fordemodulating data. In some examples, the reference signal patternmanager 1015 may receive, from the base station, an indication of areference signal pattern of a reference signal for demodulating data,the reference signal pattern being based on the assistance information.

In some examples, the reference signal pattern manager 1015 maydetermine a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information. In some examples, the reference signal patternmanager 1015 may determine the reference signal pattern based on therelative speed.

In some examples, the reference signal pattern manager 1015 may receive,from the second wireless device, an indication of the reference signalpattern. In some examples, the reference signal pattern manager 1015 maydetermine the reference signal pattern based on the indication. In someexamples, the reference signal pattern manager 1015 may receive, from aset of wireless devices, respective indications of one or more referencesignal patterns.

In some examples, the reference signal pattern manager 1015 maydetermine the reference signal pattern based on the one or morereference signal patterns. In some examples, the reference signalpattern manager 1015 may select the reference signal pattern from one ormore reference signal patterns, each of the one or more reference signalpatterns corresponding to a respective relative speed, or a range ofrelative speeds, or a combination thereof.

In some examples, the reference signal pattern manager 1015 may identifya configuration of a map between the each of the one or more referencesignal patterns and the respective relative speed, or the range ofrelative speeds, or a combination thereof. In some examples, thereference signal pattern manager 1015 may determine the reference signalpattern based on the relative speeds of the set of communication links.In some examples, the reference signal pattern manager 1015 maydetermine the reference signal pattern based on the subcarrier spacingand a relative speed between the first wireless device and the secondwireless device.

In some examples, the reference signal pattern manager 1015 may identifya difference between the first assistance information and the secondassistance information. In some examples, the reference signal patternmanager 1015 may determine the reference signal pattern based on thedifference. In some examples, the reference signal pattern manager 1015may transmit an indication of the reference signal pattern to the one ormore other wireless devices.

In some examples, the reference signal pattern manager 1015 maydetermine the reference signal pattern based on the error ratesatisfying an error rate threshold. In some examples, the referencesignal pattern manager 1015 may determine the reference signal patternbased on the received power satisfying a power threshold. In some cases,the reference signal pattern is based on a map between the one or morereference signal patterns and a respective relative speed, or a range ofrelative speeds, or a combination thereof, and where the referencesignal pattern is determined based on the map and the subcarrierspacing.

In some cases, the reference signal pattern indicates one or more symbolperiods during which the reference signal is transmitted and a gapbetween each of the one or more symbol periods. In some cases, thereference signal pattern is from a set of reference signal patterns,each reference signal pattern of the set including a different number ofsymbol periods within a slot that include the reference signal.

In some cases, the reference signal pattern is from a set of referencesignal patterns, each reference signal pattern of the set including adifferent gap between symbol periods within a slot that include thereference signal. In some cases, the indication is transmitted withincontrol information to the one or more other wireless devices.

In some cases, the reference signal pattern is from one or morereference signal patterns, each of the one or more reference signalpatterns corresponding to a respective speed, or a range of speeds, or acombination thereof. In some cases, the reference signal patternincludes one or more symbol periods during which the reference signal istransmitted and a gap between each of the one or more symbol periods.

The speed component 1020 may determine a speed of the first wirelessdevice. In some examples, the speed component 1020 may determine thespeed of the first wireless device. In some examples, the speedcomponent 1020 may determine an absolute speed of the first wirelessdevice. In some examples, the speed component 1020 may identify thespeed value from a speed index based on the absolute speed, the speedindex including a map between respective speed values and one or moreabsolute speeds, or a range of absolute speeds, or a combinationthereof.

In some examples, the speed component 1020 may identify a configurationof the speed index, where identifying the speed value is based on theconfiguration. In some examples, the speed component 1020 may receive anindication of the configuration of the speed index. In some examples,the speed component 1020 may receive, from the second wireless device,an indication of a speed of the second wireless device, or a velocity ofthe second wireless device, or a location of the second wireless device,or a combination thereof.

In some examples, the speed component 1020 may calculate the speed ofthe second wireless device based on the one or more zones the secondwireless device was located in during the time period. In some cases,the speed index is from a set of speed indices. The communicationsmanager 1040 may transmit the data and the reference signal to the oneor more other wireless devices, the reference signal being transmittedin accordance with the reference signal pattern.

In some examples, the communications manager 1040 may transmit the dataand the reference signal to a second wireless device, the referencesignal being transmitted in accordance with the reference signalpattern. In some examples, the communications manager 1040 may transmitthe data and the reference signal to the one or more other wirelessdevices, the reference signal being transmitted in accordance with thereference signal pattern.

In some examples, the communications manager 1040 may identify a set ofcommunication links with other wireless devices, each communication linkof the set of communication links being associated with a relative speedbetween the first wireless device and a respective wireless device. Insome examples, the communications manager 1040 may determine an errorrate threshold for transmitting the data over the set of communicationlinks, where the reference signal pattern is based on the relativespeeds of the set of communication links and the error rate threshold.

In some examples, the communications manager 1040 may transmit the dataand the reference signal to the second wireless device, the referencesignal being transmitted in accordance with the reference signalpattern. In some examples, the communications manager 1040 may receivethe data and the reference signal from the second wireless device, thereference signal being received in accordance with the reference signalpattern.

In some examples, communicating with the second wireless device usingsidelink communications, where the first wireless device includes afirst UE and the second wireless device includes a second UE. In someexamples, the communications manager 1040 may broadcast the data and thereference signal to the one or more other wireless devices.

In some examples, operating under a mode for sidelink communications,where the first wireless device includes a first UE and the secondwireless device includes a second UE.

The subcarrier spacing component 1045 may identify a subcarrier spacingfor communicating with one or more other wireless devices. In someexamples, the subcarrier spacing component 1045 may identify asubcarrier spacing for communicating with the second wireless device.

The feedback component 1055 may receive, from one or more other wirelessdevices, feedback information in response to one or more previous datatransmissions to the one or more other wireless devices. In someexamples, the feedback component 1055 may compute an error rate over atime period based on the feedback information. In some examples, thefeedback component 1055 may measure a received power of the feedbackinformation.

In some cases, the error rate includes a block error rate or a packeterror rate of the one or more previous data transmissions. In somecases, the feedback information includes one or more negativeacknowledgments received during a time period. The direction component1025 may determine a movement direction of the first wireless device.

In some examples, the direction component 1025 may determine an absolutemovement direction of the first wireless device. In some examples, thedirection component 1025 may identify the direction value from adirection index based on the absolute movement direction, the directionindex including a map between one or more absolute movement directionsand respective direction values.

In some cases, each of the respective direction values are based on anangular offset from a cardinal direction or an intercardinal direction.The location component 1030 may determine the location of the firstwireless device. In some examples, identifying a zone identifier from aset of zone identifiers based on the location of the first wirelessdevice, each of the set of zone identifiers being associated with arespective geographic area, where the location value includes the zoneidentifier.

In some examples, determining, based on the location of the secondwireless device, one or more zones the second wireless device waslocated in during a time period, where the received indication includesone or more zone identifiers corresponding to respective zones.

The relative speed manager 1035 may identify a relative speed betweenthe first wireless device and the second wireless device based on theassistance information, where the reference signal pattern is determinedbased on the relative speed.

In some examples, the relative speed manager 1035 may determine therelative speed based on the received indication. In some examples, therelative speed manager 1035 may calculate the relative speed based onthe speed of the first wireless device and the speed of the secondwireless device. In some examples, the relative speed manager 1035 maycalculate the relative speed based on the velocity of the first wirelessdevice and the velocity of the second wireless device. The memory 1050may store the first assistance information and the second assistanceinformation at the first wireless device.

FIG. 11 shows a diagram of a system 1100 including a device 1105 thatsupports reference signal patterns based on relative speed between atransmitter and receiver in accordance with one or more aspects of thepresent disclosure. The device 1105 may be an example of or include thecomponents of device 805, device 905, or a UE 115 as described herein.The device 1105 may include components for bi-directional voice and datacommunications including components for transmitting and receivingcommunications, including a reference signal manager 1110, an I/Ocontroller 1115, a transceiver 1120, an antenna 1125, memory 1130, and aprocessor 1140. These components may be in electronic communication viaone or more buses (e.g., bus 1145).

The reference signal manager 1110 may transmit assistance information toa second wireless device, the assistance information associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof and identify a reference signal patternof a reference signal for demodulating data, the reference signalpattern based on the assistance information. The reference signalmanager 1110 may also determine a speed of the first wireless device,identify a subcarrier spacing for communicating with one or more otherwireless devices, determine, based on the speed of the first wirelessdevice and the subcarrier spacing, a reference signal pattern of areference signal for demodulating data, and transmit the data and thereference signal to the one or more other wireless devices, thereference signal being transmitted in accordance with the referencesignal pattern. The reference signal manager 1110 may also transmitassistance information to a base station, the assistance informationassociated with a speed of the first wireless device, or a location ofthe first wireless device, or a combination thereof, receive, from thebase station, an indication of a reference signal pattern of a referencesignal for demodulating data, the reference signal pattern being basedon the assistance information, and transmit the data and the referencesignal to a second wireless device, the reference signal beingtransmitted in accordance with the reference signal pattern. Thereference signal manager 1110 may also receive, from one or more otherwireless devices, feedback information in response to one or moreprevious data transmissions to the one or more other wireless devices,determine a reference signal pattern of a reference signal fordemodulating data, the reference signal pattern being based on thefeedback information, and transmit the data and the reference signal tothe one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

The I/O controller 1115 may manage input and output signals for thedevice 1105. The I/O controller 1115 may also manage peripherals notintegrated into the device 1105. In some cases, the I/O controller 1115may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 1115 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 1115may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 1115may be implemented as part of a processor. In some cases, a user mayinteract with the device 1105 via the I/O controller 1115 or viahardware components controlled by the I/O controller 1115.

The transceiver 1120 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described herein. For example, thetransceiver 1120 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1120 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125.However, in some cases, the device may have more than one antenna 1125,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1130 may include random-access memory (RAM) and read-onlymemory (ROM). The memory 1130 may store computer-readable,computer-executable code 1135 including instructions that, whenexecuted, cause the processor to perform various functions describedherein. In some cases, the memory 1130 may contain, among other things,a basic input/output system (BIOS) which may control basic hardware orsoftware operation such as the interaction with peripheral components ordevices.

The processor 1140 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1140 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 1140. The processor 1140 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 1130) to cause the device 1105 to perform variousfunctions (e.g., functions or tasks supporting reference signal patternsbased on relative speed between a transmitter and receiver).

The code 1135 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1135 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1135 may not be directly executable by theprocessor 1140 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 12 shows a flowchart illustrating a method 1200 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1200 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1200 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1205, the UE may transmit assistance information to a second wirelessdevice. For example, the assistance information may be associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof. The operations of 1205 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1205 may be performed by a mobility manageras described with reference to FIGS. 8 through 11 .

At 1210, the UE may determine an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern based on the assistance information. The operations of 1210 maybe performed according to the methods described herein. In someexamples, aspects of the operations of 1210 may be performed by areference signal pattern manager as described with reference to FIGS. 8through 11 .

FIG. 13 shows a flowchart illustrating a method 1300 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1300 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1300 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1305, the UE may transmit assistance information to a second wirelessdevice. For example, the assistance information may be associated with aspeed of the first wireless device (e.g., the UE), or a location of thefirst wireless device, or a combination thereof. The operations of 1305may be performed according to the methods described herein. In someexamples, aspects of the operations of 1305 may be performed by amobility manager as described with reference to FIGS. 8 through 11 .

At 1310, the UE may identify a relative speed between the first wirelessdevice and the second wireless device based on the assistanceinformation. The operations of 1310 may be performed according to themethods described herein. In some examples, aspects of the operations of1310 may be performed by a relative speed manager as described withreference to FIGS. 8 through 11 .

At 1315, the UE may determine an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern based on the assistance information and the relative speed. Theoperations of 1315 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1315 may beperformed by a reference signal pattern manager as described withreference to FIGS. 8 through 11 .

FIG. 14 shows a flowchart illustrating a method 1400 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1400 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1400 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1405, the UE may determine the speed of a first wireless device(e.g., the UE). The operations of 1405 may be performed according to themethods described herein. In some examples, aspects of the operations of1405 may be performed by a speed component as described with referenceto FIGS. 8 through 11 .

At 1410, the UE may determine a movement direction of the first wirelessdevice. The operations of 1410 may be performed according to the methodsdescribed herein. In some examples, aspects of the operations of 1410may be performed by a direction component as described with reference toFIGS. 8 through 11 .

At 1415, the UE may transmit assistance information to a second wirelessdevice (e.g., another UE), the assistance information associated with aspeed of the first wireless device, or a location of the first wirelessdevice, or a combination thereof. The operations of 1415 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1415 may be performed by a mobility manageras described with reference to FIGS. 8 through 11 .

At 1420, the UE may transmit, as part of the assistance information, aspeed value indicating the speed of the first wireless device. Theoperations of 1420 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1420 may beperformed by a mobility manager as described with reference to FIGS. 8through 11 .

At 1425, the UE may also transmit, as part of the assistanceinformation, a direction value indicating the movement direction of thefirst wireless device. That is, the UE may options transmit speedinformation, or both speed and movement direction information within theassistance information. The operations of 1425 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1425 may be performed by a mobility manager asdescribed with reference to FIGS. 8 through 11 .

At 1430, the UE may determine an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern based on the assistance information. The operations of 1430 maybe performed according to the methods described herein. In someexamples, aspects of the operations of 1430 may be performed by areference signal pattern manager as described with reference to FIGS. 8through 11 .

FIG. 15 shows a flowchart illustrating a method 1500 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1500 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1500 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1505, the UE may determine the location of a first wireless device(e.g., the UE). The operations of 1505 may be performed according to themethods described herein. In some examples, aspects of the operations of1505 may be performed by a location component as described withreference to FIGS. 8 through 11 .

At 1510, the UE may transmit assistance information to a second wirelessdevice, the assistance information associated with a speed of the firstwireless device, or a location of the first wireless device, or acombination thereof. The operations of 1510 may be performed accordingto the methods described herein. In some examples, aspects of theoperations of 1510 may be performed by a mobility manager as describedwith reference to FIGS. 8 through 11 .

At 1515, the UE may transmit, as part of the assistance information, alocation value indicating the location of the first wireless device. Theoperations of 1515 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1515 may beperformed by a mobility manager as described with reference to FIGS. 8through 11 .

At 1520, the UE may determine an adaptive reference signal pattern of areference signal for demodulating data, the adaptive reference signalpattern based on the assistance information. The operations of 1520 maybe performed according to the methods described herein. In someexamples, aspects of the operations of 1520 may be performed by areference signal pattern manager as described with reference to FIGS. 8through 11 .

FIG. 16 shows a flowchart illustrating a method 1600 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1600 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1600 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1605, the UE may determine a speed of the first wireless device(e.g., the UE). The operations of 1605 may be performed according to themethods described herein. In some examples, aspects of the operations of1605 may be performed by a speed component as described with referenceto FIGS. 8 through 11 .

At 1610, the UE may identify a subcarrier spacing for communicating withone or more other wireless devices. The operations of 1610 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1610 may be performed by a subcarrierspacing component as described with reference to FIGS. 8 through 11 .

At 1615, the UE may determine, based on the speed of the first wirelessdevice and the subcarrier spacing, a reference signal pattern of areference signal for demodulating data. The operations of 1615 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1615 may be performed by a reference signalpattern manager as described with reference to FIGS. 8 through 11 .

At 1620, the UE may transmit the data and the reference signal to theone or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern. Theoperations of 1620 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1620 may beperformed by a communications manager as described with reference toFIGS. 8 through 11 .

FIG. 17 shows a flowchart illustrating a method 1700 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1700 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1700 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1705, the UE may transmit assistance information to a base station.For example, the assistance information may be associated with a speedof the first wireless device (e.g., the UE), or a location of the firstwireless device, or a combination thereof. The operations of 1705 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1705 may be performed by a mobility manageras described with reference to FIGS. 8 through 11 .

At 1710, the UE may receive, from the base station, an indication of anadaptive reference signal pattern of a reference signal for demodulatingdata, the adaptive reference signal pattern being based on theassistance information. The operations of 1710 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1710 may be performed by a reference signal patternmanager as described with reference to FIGS. 8 through 11 .

At 1715, the UE may transmit the data and the reference signal to asecond wireless device, the reference signal being transmitted inaccordance with the adaptive reference signal pattern. The operations of1715 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1715 may be performed by acommunications manager as described with reference to FIGS. 8 through 11.

FIG. 18 shows a flowchart illustrating a method 1800 that supportsreference signal patterns based on relative speed between a transmitterand receiver in accordance with one or more aspects of the presentdisclosure. The operations of method 1800 may be implemented by a UE 115or its components as described herein. For example, the operations ofmethod 1800 may be performed by a reference signal manager as describedwith reference to FIGS. 8 through 11 . In some examples, a UE mayexecute a set of instructions to control the functional elements of theUE to perform the functions described herein. Additionally oralternatively, a UE may perform aspects of the functions describedherein using special-purpose hardware.

At 1805, the UE may receive, from one or more other wireless devices,feedback information in response to one or more previous datatransmissions to the one or more other wireless devices. The operationsof 1805 may be performed according to the methods described herein. Insome examples, aspects of the operations of 1805 may be performed by afeedback component as described with reference to FIGS. 8 through 11 .

At 1810, the UE may determine a reference signal pattern of a referencesignal for demodulating data, the reference signal pattern being basedon the feedback information. The operations of 1810 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1810 may be performed by a reference signal patternmanager as described with reference to FIGS. 8 through 11 .

At 1815, the UE may transmit the data and the reference signal to theone or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern. Theoperations of 1815 may be performed according to the methods describedherein. In some examples, aspects of the operations of 1815 may beperformed by a communications manager as described with reference toFIGS. 8 through 11 .

The following provides an overview of examples of the presentdisclosure:

Example 1: A method for wireless communications at a first wirelessdevice comprising: transmitting assistance information to a secondwireless device; and determining an adaptive reference signal pattern ofa reference signal for demodulating data, the adaptive reference signalpattern based at least in part on the assistance information.

Example 2: The method of example 1, further comprising: determining aspeed of the first wireless device; and transmitting, as part of theassistance information, a speed value indicating the speed of the firstwireless device.

Example 3: The method of any one of examples 1 and 2, furthercomprising: determining a movement direction of the first wirelessdevice; and transmitting, as part of the assistance information, adirection value indicating the movement direction of the first wirelessdevice.

Example 4: The method of any one of examples 1 and 2, furthercomprising: determining an absolute speed of the first wireless device;and identifying the speed value from a speed index based at least inpart on the absolute speed, the speed index comprising a map betweenrespective speed values and one or more absolute speeds, or a range ofabsolute speeds, or a combination thereof.

Example 5: The method of any one of examples 1 through 4, furthercomprising: determining a location of the first wireless device; andtransmitting, as part of the assistance information, a location valueindicating the location of the first wireless device.

Example 6: The method of any one of examples 1 through 5, furthercomprising: identifying a relative speed between the first wirelessdevice and the second wireless device based at least in part on theassistance information, wherein the adaptive reference signal pattern isdetermined based at least in part on the relative speed.

Example 7: The method of example 1 through 6, wherein identifying therelative speed comprises: receiving, from the second wireless device, anindication of a speed of the second wireless device, or a velocity ofthe second wireless device, or a location of the second wireless device,or a combination thereof; and determining the relative speed based atleast in part on the indication.

Example 8: The method of any one of examples 1 through 7, furthercomprising: transmitting, as part of the assistance information, anindication of the relative speed.

Example 9: The method of any one of examples 1 through 8, furthercomprising: determining the adaptive reference signal pattern based atleast in part on the relative speed; and transmitting, as part of theassistance information, an indication of the adaptive reference signalpattern.

Example 10: The method of any one of examples 1 through 9, whereindetermining the adaptive reference signal pattern comprises: receiving,from the second wireless device, an indication of the adaptive referencesignal pattern; and determining the adaptive reference signal patternbased at least in part on the indication.

Example 11: The method of any one of examples 1 through 10, whereindetermining the adaptive reference signal pattern comprises: receiving,from a plurality of wireless devices, respective indications of one ormore reference signal patterns; and determining the adaptive referencesignal pattern based at least in part on the one or more referencesignal patterns.

Example 12: The method of any one of examples 1 through 11, whereindetermining the adaptive reference signal pattern comprises: selectingthe adaptive reference signal pattern from one or more reference signalpatterns, each of the one or more reference signal patternscorresponding to a respective relative speed, or a range of relativespeeds, or a combination thereof.

Example 13: The method of any one of examples 1 through 12, whereindetermining the adaptive reference signal pattern comprises: identifyinga plurality of communication links with other wireless devices, eachcommunication link of the plurality of communication links beingassociated with a relative speed between the first wireless device and arespective wireless device; and determining the adaptive referencesignal pattern based at least in part on the relative speeds of theplurality of communication links.

Example 14: The method of any one of examples 1 through 13, whereindetermining the adaptive reference signal pattern comprises: identifyinga subcarrier spacing for communicating with the second wireless device;and determining the adaptive reference signal pattern based at least inpart on the subcarrier spacing and a relative speed between the firstwireless device and the second wireless device.

Example 15: The method of any one of examples 1 through 14, furthercomprising: receiving first assistance information and second assistanceinformation from the second wireless device, each of the firstassistance information and the second assistance information beingassociated with a respective speed of the second wireless device, or arespective location of the second wireless device, or a combinationthereof; storing the first assistance information and the secondassistance information at the first wireless device; identifying adifference between the first assistance information and the secondassistance information; and determining the adaptive reference signalpattern based at least in part on the difference.

Example 16: The method of any one of examples 1 through 15, furthercomprising: generating first assistance information and secondassistance information for the first wireless device, each of the firstassistance information and the second assistance information beingassociated with a respective speed of the first wireless device, or arespective location of the first wireless device, or a combinationthereof; identifying a difference between the first assistanceinformation and the second assistance information; and transmitting theassistance information based at least in part on identifying thedifference.

Example 17: The method of any one of examples 1 through 16, furthercomprising: identifying a periodicity for transmitting the assistanceinformation, wherein the assistance information is transmitted inaccordance with the periodicity.

Example 18: The method of any one of examples 1 through 17, furthercomprising: receiving a request to transmit the assistance information,wherein the assistance information is transmitted in response to therequest.

Example 19: The method of any one of examples 1 through 18, furthercomprising: transmitting the data and the reference signal to the secondwireless device, the reference signal being transmitted in accordancewith the adaptive reference signal pattern, wherein the adaptivereference signal pattern indicates one or more symbol periods duringwhich the reference signal is transmitted and a gap between each of theone or more symbol periods.

Example 20: The method of any one of examples 1 through 19, furthercomprising: receiving the data and the reference signal from the secondwireless device, the reference signal being received in accordance withthe adaptive reference signal pattern, wherein the adaptive referencesignal pattern indicates one or more symbol periods during which thereference signal is transmitted and a gap between each of the one ormore symbol periods.

Example 21: The method of any one of examples 1 through 20, furthercomprising: communicating with the second wireless device using sidelinkcommunications, wherein the first wireless device comprises a first userequipment (UE) and the second wireless device comprises a second UE.

Example 22: The method of any one of examples 1 through 21, wherein thesidelink communications comprise vehicle to everything communications.

Example 23: A method for wireless communications at a first wirelessdevice, comprising: determining a speed of the first wireless device;identifying a subcarrier spacing for communicating with one or moreother wireless devices; determining, based at least in part on the speedof the first wireless device and the subcarrier spacing, a referencesignal pattern of a reference signal for demodulating data; andtransmitting the data and the reference signal to the one or more otherwireless devices, the reference signal being transmitted in accordancewith the reference signal pattern.

Example 24: The method of example 23, wherein transmitting the data andindication of the reference signal pattern comprises: broadcasting thedata and the reference signal to the one or more other wireless devices.

Example 25: The method of any one of examples 23 and 24, furthercomprising: transmitting an indication of the reference signal patternto the one or more other wireless devices.

Example 26: A method for wireless communications at a first wirelessdevice comprising: transmitting assistance information to a basestation; receiving, from the base station, an indication of an adaptivereference signal pattern of a reference signal for demodulating data,the adaptive reference signal pattern being based at least in part onthe assistance information; and transmitting the data and the referencesignal to a second wireless device, the reference signal beingtransmitted in accordance with the adaptive reference signal pattern.

Example 27: The method of example 26, wherein the adaptive referencesignal pattern is from one or more reference signal patterns, each ofthe one or more reference signal patterns corresponding to a respectivespeed, or a range of speeds, or a combination thereof.

Example 28: The method of any one of examples 26 and 27, wherein theadaptive reference signal pattern comprises one or more symbol periodsduring which the reference signal is transmitted and a gap between eachof the one or more symbol periods.

Example 29: A method for wireless communications at a first wirelessdevice, comprising: receiving, from one or more other wireless devices,feedback information in response to one or more previous datatransmissions to the one or more other wireless devices; determining areference signal pattern of a reference signal for demodulating data,the reference signal pattern being based at least in part on thefeedback information; and transmitting the data and the reference signalto the one or more other wireless devices, the reference signal beingtransmitted in accordance with the reference signal pattern.

Example 30: The method of example 29, wherein determining the referencesignal pattern comprises: computing an error rate over a time periodbased at least in part on the feedback information; and determining thereference signal pattern based at least in part on the error ratesatisfying an error rate threshold.

Example 31: An apparatus for wireless communication comprising at leastone means for performing a method of any one of examples 1 through 22.

Example 32: An apparatus for wireless communication comprising aprocessor, and memory coupled to the processor, and the processor andmemory may be configured to cause the apparatus to perform a method ofany one of examples 1 through 22.

Example 33: A non-transitory computer-readable medium storing code forwireless communication comprising a processor, memory in electroniccommunication with the processor, and instructions executable by theprocessor to cause the apparatus to perform a method of any one ofexamples 1 through 22.

Example 34: An apparatus for wireless communication comprising at leastone means for performing a method of any one of examples 23 through 25.

Example 35: An apparatus for wireless communication comprising aprocessor, and memory coupled to the processor, and the processor andmemory may be configured to cause the apparatus to perform a method ofany one of examples 23 through 25.

Example 36: A non-transitory computer-readable medium storing code forwireless communication comprising a processor, memory in electroniccommunication with the processor, and instructions executable by theprocessor to cause the apparatus to perform a method of any one ofexamples 23 through 25.

Example 37: An apparatus for wireless communication comprising at leastone means for performing a method of any one of examples 26 through 28.

Example 38: An apparatus for wireless communication comprising aprocessor, and memory coupled to the processor, and the processor andmemory may be configured to cause the apparatus to perform a method ofany one of examples 26 through 28.

Example 39: A non-transitory computer-readable medium storing code forwireless communication comprising a processor, memory in electroniccommunication with the processor, and instructions executable by theprocessor to cause the apparatus to perform a method of any one ofexamples 26 through 28.

Example 40: An apparatus for wireless communication comprising at leastone means for performing a method of any one of examples 29 and 30.

Example 41: An apparatus for wireless communication comprising aprocessor, and memory coupled to the processor, and the processor andmemory may be configured to cause the apparatus to perform a method ofany one of examples 29 and 30.

Example 42: A non-transitory computer-readable medium storing code forwireless communication comprising a processor, memory in electroniccommunication with the processor, and instructions executable by theprocessor to cause the apparatus to perform a method of any one ofexamples 29 and 30.

It should be noted that the methods described herein describe possibleimplementations, and that the operations may be rearranged or otherwisemodified and that other implementations are possible. Further, aspectsfrom two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned herein as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell maybe associated with a lower-powered base station, as compared with amacro cell, and a small cell may operate in the same or different (e.g.,licensed, unlicensed, etc.) frequency bands as macro cells. Small cellsmay include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs with service subscriptionswith the network provider. A femto cell may also cover a smallgeographic area (e.g., a home) and may provide restricted access by UEshaving an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a smallcell may be referred to as a small cell eNB, a pico eNB, a femto eNB, ora home eNB. An eNB may support one or multiple (e.g., two, three, four,and the like) cells, and may also support communications using one ormultiple component carriers.

The wireless communications systems described herein may supportsynchronous or asynchronous operation. For synchronous operation, thebase stations may have similar frame timing, and transmissions fromdifferent base stations may be approximately aligned in time. Forasynchronous operation, the base stations may have different frametiming, and transmissions from different base stations may not bealigned in time. The techniques described herein may be used for eithersynchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA, or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices(e.g., a combination of a DSP and a microprocessor, multiplemicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described herein can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROMor other optical disk storage, magnetic disk storage or other magneticstorage devices, or any other non-transitory medium that can be used tocarry or store desired program code means in the form of instructions ordata structures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, include CD, laser disc, optical disc,digital versatile disc (DVD), floppy disk and Blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary feature that is described as “based oncondition A” may be based on both a condition A and a condition Bwithout departing from the scope of the present disclosure. In otherwords, as used herein, the phrase “based on” shall be construed in thesame manner as the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. An apparatus for wireless communications at afirst wireless device, comprising: a processor; and memory coupled withthe processor, the processor configured to: determine a speed of thefirst wireless device; identify a subcarrier spacing for communicationswith one or more other wireless devices; determine, based at least inpart on the speed of the first wireless device and the subcarrierspacing, a reference signal pattern of a reference signal fordemodulation of data; and transmit the data and the reference signal tothe one or more other wireless devices, wherein the reference signal istransmitted in accordance with the reference signal pattern.
 2. Theapparatus of claim 1, wherein, to transmit the data and the referencesignal, the processor is configured to: broadcast the data and thereference signal to the one or more other wireless devices.
 3. Theapparatus of claim 1, wherein the processor is further configured to:transmit an indication of the reference signal pattern to the one ormore other wireless devices.
 4. The apparatus of claim 3, wherein theindication of the reference signal pattern is transmitted via a sidelinkcontrol information message.
 5. The apparatus of claim 1, wherein, todetermine the reference signal pattern of the reference signal, theprocessor is configured to: select the reference signal pattern from oneor more reference signal patterns, each of the one or more referencesignal patterns corresponding to a respective speed, a range of speeds,or a combination thereof.
 6. The apparatus of claim 1, wherein theprocessor is further configured to: determine a direction of the firstwireless device, wherein the reference signal pattern is based at leastin part on the direction.
 7. The apparatus of claim 1, wherein theprocessor is further configured to: determine that the first wirelessdevice is unable to receive assistance information from the one or moreother wireless devices, wherein the speed, the subcarrier spacing, thereference signal pattern, or any combination thereof, is determinedbased on the first wireless device being unable to receive assistanceinformation from the one or more other wireless devices.
 8. Theapparatus of claim 7, wherein the processor is further configured to:estimate an additional speed, a direction, or both, of the one or moreother wireless devices based at least in part on the first wirelessdevice being unable to receive assistance information from the one ormore other wireless devices, wherein the reference signal pattern isbased at least in part on the additional speed, the direction, or both.9. The apparatus of claim 1, wherein the reference signal patterncomprises a demodulation reference signal pattern, and wherein thereference signal comprises a demodulation reference signal.
 10. Anapparatus for wireless communications at a first wireless devicecomprising: a processor; and memory coupled with the processor, theprocessor configured to: transmit assistance information; receive anindication of an adaptive reference signal pattern of a reference signalfor demodulation of data, the adaptive reference signal pattern based atleast in part on the assistance information; and transmit the data andthe reference signal to a second wireless device, the reference signalbeing transmitted in accordance with the adaptive reference signalpattern.
 11. The apparatus of claim 10, wherein the processor is furtherconfigured to: receive control signaling that indicates a tableincluding a plurality of mappings between reference signal patternindices and adaptive reference signal patterns, wherein the indicationof the adaptive reference signal pattern comprises a reference signalpattern index; and map the reference signal pattern index to theadaptive reference signal pattern in accordance with the table based atleast in part on the plurality of mappings of the table.
 12. Theapparatus of claim 11, wherein the control signaling comprises radioresource control signaling.
 13. The apparatus of claim 10, wherein theassistance information indicates one or more parameters including aspeed of the first wireless device, a relative speed of the firstwireless device relative to a second wireless device, a direction of thefirst wireless device, a location of the first wireless device, asubcarrier spacing, a reference pattern index, or any combinationthereof, wherein the adaptive reference signal pattern is based at leastin part on the one or more parameters.
 14. The apparatus of claim 10,wherein the adaptive reference signal pattern is from one or morereference signal patterns, each of the one or more reference signalpatterns corresponding to a respective speed, or a range of speeds, or acombination thereof.
 15. The apparatus of claim 10, wherein the adaptivereference signal pattern comprises one or more symbol periods duringwhich the reference signal is transmitted and a gap between each of theone or more symbol periods.
 16. The apparatus of claim 10, wherein theadaptive reference signal pattern comprises a demodulation referencesignal pattern, and wherein the reference signal comprises ademodulation reference signal.
 17. An apparatus for wirelesscommunications at a first wireless device, comprising: a processor; andmemory coupled with the processor, the processor configured to: receive,from one or more other wireless devices, feedback information inresponse to one or more previous data transmissions to the one or moreother wireless devices; determine a reference signal pattern of areference signal for demodulation of data, the reference signal patternbeing based at least in part on the feedback information; and transmitthe data and the reference signal to the one or more other wirelessdevices, wherein the reference signal is transmitted in accordance withthe reference signal pattern.
 18. The apparatus of claim 17, wherein, todetermine the reference signal pattern, the processor is configured to:compute an error rate over a time period based at least in part on thefeedback information; and determine the reference signal pattern basedat least in part on a satisfaction of an error rate threshold by theerror rate.
 19. The apparatus of claim 18, wherein the error ratecomprises a block error rate, a packet error, or both.
 20. The apparatusof claim 17, wherein, to determine the reference signal pattern, theprocessor is configured to: determine a received power associated withthe feedback information; and determine the reference signal patternbased at least in part on a satisfaction of a power threshold by thereceived power.
 21. The apparatus of claim 17, wherein, to determine thereference signal pattern, the processor is configured to: compute anerror rate over a time period based at least in part on the feedbackinformation; determine a received power associated with the feedbackinformation over the time period; and determine the reference signalpattern based at least in part on a satisfaction of an error ratethreshold and a power threshold by the error rate and the receivedpower, respectively.
 22. The apparatus of claim 17, wherein thereference signal pattern comprises a demodulation reference signalpattern, and wherein the reference signal comprises a demodulationreference signal.
 23. A method for wireless communications at a firstwireless device, comprising: determining a speed of the first wirelessdevice; identifying a subcarrier spacing for communications with one ormore other wireless devices; determining, based at least in part on thespeed of the first wireless device and the subcarrier spacing, areference signal pattern of a reference signal for demodulating data;and transmitting the data and the reference signal to the one or moreother wireless devices, wherein the reference signal is transmitted inaccordance with the reference signal pattern.
 24. The method of claim23, wherein transmitting the data and the reference signal comprises:broadcasting the data and the reference signal to the one or more otherwireless devices.
 25. The method of claim 23, further comprising:transmitting an indication of the reference signal pattern to the one ormore other wireless devices.
 26. The method of claim 25, wherein theindication of the reference signal pattern is transmitted via a sidelinkcontrol information message.
 27. The method of claim 23, whereindetermining the reference signal pattern of the reference signalcomprises: selecting the reference signal pattern from one or morereference signal patterns, each of the one or more reference signalpatterns corresponding to a respective speed, a range of speeds, or acombination thereof.
 28. The method of claim 23, further comprising:determining a direction of the first wireless device, wherein thereference signal pattern is based at least in part on the direction. 29.The method of claim 23, further comprising: determining that the firstwireless device is unable to receive assistance information from the oneor more other wireless devices, wherein determining the speed,identifying the subcarrier spacing, determining the reference signalpattern, or any combination thereof, is based on the first wirelessdevice being unable to receive assistance information from the one ormore other wireless devices.
 30. The method of claim 29, furthercomprising: estimating an additional speed, a direction, or both, of theone or more other wireless devices based at least in part on the firstwireless device being unable to receive assistance information from theone or more other wireless devices, wherein the reference signal patternis based at least in part on the additional speed, the direction, orboth.